If you have a MicroSD card installed then check if it is either incorrectly installed, shorted out, or an improper size for the device. This problem has been reported as well from downloading a corrupted song or application onto your storage device. If nothing else then you can try deleting all the songs/apps on the external SD card and slowly re-adding them to it in order to figure out which one is messed up.
If this doesn't solve your problems, then I would suggest backing up all of your data with Samsung Kies and then doing a factory reset of the phone to fix the issue. http://www.samsung.com/us/support/owners/product/SGH-T989ZKBTMB <--This version is the latest installer, but you will need to update it for a minute or two before using it. This will also be how you can most easily update your Samsung Galaxy S2 to the current version, as well as the Ice Cream Sandwich (Android 4.0) update coming out approximately tomorrow.
This has happened to me in the past. Turning off the service in app manager will only provide a bandaid to the issue. It took me for ever to find out what was going on. Even after master resets and trying different roms (for those with root). I would say its most likely a corrupt file (picture, download etc..) in ur SD card or in ur device memory. One way to see if this is the case:
1 - Remove all content from internal and external storage (save it to ur desktop)
2 - Delete all content on ur internal and external storage (after u have done step number 1.)
3 - Reboot Device
4 - Scanning should take a few minutes max
5 - If issue is resolved, start loading the content back on folder by folder till you can find the corrupt source.
6 - Trust me... its a tedious task..
Try this first,
Delete the last video or photo you have taken. Then see if it still says the same, if yes... work your way though deleting photos and videos until it no longer tells you about scanner process. Once the problem file is found simply reload saved images from pc backup minus corrupt file.
Or you can delete images and videos untill you know that it was working ok untill that day