The entire issue relating to the 'low on space' message relates to available System Memory. So, first -- yes, the message is unfortunately somewhat misleading.
Second, the total System Memory in the GARMINfone is only 155 MB; This was probably very low even at the time the GARMINfone was initially released. For comparison, today's smartphones frequently have up to 1 GB of System Memory. Think of System Memory as RAM. And, just like on a PC or a MAC, a lot of apps are loaded into RAM when you boot up. These include just about every app on your GARMINfone that routinely polls for information via the internet, e.g., your e-mail app. Even if you use an app killer, most of the memory-resident components of these apps will be reloaded into System Memory quite quickly. Running a weather app, g-mail, instant messaging, the clock (with alarms), the calendar (with appointment notifications), Skype, or a To-Do list app? They're chewing up System Memory. (And note, I didn't even get to Facebook, Youtube, Twitter, Myspace, which I don't use either and would dearly love to be able to remove.)
Third, I'm presuming you've set Default Storage (under Settings) to the SD Card, not Internal Storage. Indeed, any time you install a new app and are given the option, always point it to the SD Card, not internal storage. Internal storage is fixed; you can always install a larger SD card. (Actually, that's a micro SDHC card in case you want to go there.)
Fourth, it looks like you've done everything possible to solve this problem short of a Master Reset -- so, unfortunately, it's probably time for you to do that. However, before you do this, carefully read through the other posts in this thread and take note of all the information that you should note down in order to bring your device back up with minimal inconvenience. In particular, if you've unlocked your GARMINfone, make sure you've got a record of the unlock code for your fone before you start!. It's different for every GARMINfone, unlike many other smartphones. And a Master Reset will lock the GARMINfone again (again contrary to the situation with many other smartphones).
Fifth, if you install an app and subsequently decide you don't want it, always remove it through the Android Market app (and frankly that's one of the reasons I don't acquire through the Amazon marketplace). Space reservations in System Memory apparently don't get cleared if you do it some other way, so you don't end up freeing up more memory.
Sixth, since I did my Master Reset back in early December, I've found that the memory manager seems to be working better. That is, when I remove an app, it really does tend to free up System Memory. Don't ask me why this is, I don't know.
Seventh, if you've got (and use) GARMIN maps, check them immediately afterwards to ensure they're still working correctly. That seems to have been an emerging problem and I've got problems with my UK/EU maps. If you've got a problem get on it right then, don't wait until you need the maps.
Finally, and as I understand it, all rooting the GARMINfone is going to accomplish for you is getting rid of those embedded apps (Twitter, Myspace, etc., that you don't use); you're not going to be able to upgrade to Android 2.2 or 2.3 because (again, as I understand it), the hardware architecture of the GARMINfone is not adequate to support the functionality. Indeed, as it is, upgrading the GARMINfone from Android 1.6 to 2.1 was apparently a major undertaking and you have a very customized version of 2.1 running on the GARMINfone.
Hope this helps.
You and I did the Master Reset at just about the same time. It seems to me that, for some inexplicable reason, the memory management is now better than it was before the Master Reset. What's your experience been?
I've actually overstuffed the phone (more apps than before) but memory, after soaring briefly to 85% used, has settled back down and stays in the mid-70% range now -- no adverse effects.
I've not been any more impressed with the memory management after the reset. It seems the best way to fill up memory is to add and subtract apps (which I did a whole lot at first). Now that I've found the set I more or less like, I've not been adding apps and the memory has "settled down". My guess is if I started adding/subtracting apps again, I would fill up memory again. I've added/subtracted a few apps (mainly train apps for the places I've visited), and the memory has crept up to 44%. The problem seems to be when you delete an app, it's memory footprint really does not go away. I think your "problem" is that you are no longer adding/subtracting apps as much as you did when you first got the phone. I know I've been more selective with apps. All I know is when I delete an app that took up a lot of memory, the memory usage doesn't go down once the program is "gone". Any loaded program seems to leave its mark on memory long after it was removed.
Of course, if you've been deleting as many apps as you've added and your memory is doing fine, then there goes my perfectly logical theory down the toilet .
After my master reset I imported contacts from the SD and installed 3 or 4 apps Until.. phone bogged down and I got the Low on Space icon again. After deleting ALL of the apps I installed through the market app, which is said to uninstall apps more efficiently, the phone still did not have significant memory available.
So master reset again and leaving it alone, no apps just contacts and texts for this phone.
Rooting the phone seems to not be easy/possible with the android 2.1 update