Sounds like you REALLY hate swype. I don't think you can completely remove it unless you root your phone which will allow you to access and alter system apps. As for the physical keyboard predictive text, I have the same problem. It's almost like there's a very specific formula/sequence of button pushes I have to execute to get it to work, but even then it's not 100%.
I just got my new myTouch 4G Slide last night and I HATE swype, is there any way to turn it off so it's not even an option in the input menu?
See my response in the thread on bloatware http://support.t-mobile.com/message/24206#24206
The method can be used to uninstall anything that is pre-installed including Swype.
What apps are you using where you sometimes have predictive text, but not other times?
Sometimes when I use the Facebook app with the onscreen keyboard -- the predictive bar shows when I am commenting on other people's posts, but ONLY shows for the [What's on your mind?] field after I [type at least two words, then delete the entire last word.] Since this has happened with an assortment of different onscreen keyboard apps on three different Androids -- MT3G, Moto-Defy, MT4GS -- I just assumed it's an app problem, NOT the hardware (complain to Facebook, not tMo or HTC).
If it's specific apps, neither all apps nor random -- it could easily be an app problem, NOT a phone problem.
The way I have mine set - for on-screen, I use AnySoft Keyboard because I use a lot of foreign Unicode characters; for physical keyboard, I change the Input Method to Touch Input, which gives that weird white / green / orange predictive bar.
It's an extra 3sec to do the switch, but worth it to speed up those $1.50 words and for easily misspelled words.
I agree on Swype. I thought it sounded wonderful ... then I tried it. Yuck.