I've noticed a problem in my Galaxy Pop today, that after uninstalling an app the actual free space on the device doesn't change. I have downloaded a virtual guitar of size 2.6 MB, but when I went to uninstall this app, then I was shocked to seeing that only 230 KB were freed. My question is, where are th remaining 2.3 MB? I've searched the phone and SD card but couldn't find out it where it went. It also looks like I've been lost some internal space on the phone.
It could be a cache issue. You could try downloading Astro File Manager and open it. Then go to File Manager > Pref > Cache from there click on Other Internal Caches. beyond that you will probably need to do a factory restore to retrieve all your memory.
I think that maybe the remaining 2.3 MB was data in the app. Your phone may say 'deleting this app will also delete all this data' or likewise, but sometimes it doesn't delete the data. So, if you recorded 2.3 MB of songs, this is probably hiding in your device or SD card (if applicable).
I hope this works for you!