Why am I constantly running out of space on my Galaxy S2? I have a Galaxy S2 running Android 4.1.2. It has a 12GB internal HD, and a 16GB SD card.

I keep getting errors from various programs telling me I am running out of space. BeyondPod won't download new episodes, Evernote keeps putting up a notification of a lack of space (even though it seems to be storing everything), and sometimes apps won't update.

I have tried to ensure I have no superfluous apps, and I haven't really changed the apps I use since I first ever started using the device. I keep any large files, like music collections or videos, on my SD card.

When I connect my device by USB to my Linux computer and check the properties of my 12GB HD, it says 9.9 GB is used. But if I browse the files, every folder seems to have barely kilobytes of information. 

Why is my 12GB HD filling up, and how do I clear it out so I don't get these errors?

Update: My phone is rooted, so if that is something that can help me in this situaton, then root access is available to me.
If you're getting "storage space runout" on your Samsung S2 phone, just dial *#9900# on the tablet and select option 2 “Delete dumpstate/logcat” 

It's not necessary to root your android. Restart your phone afterwards.