So, I have had Avast on my Galaxy S2 since I got the phone, and never had any problems before. Yesterday a scan found one problem, which was "invalid context during scan" in some random file on the sdcard. I chose to delete it (hoping it wasn't anything important) and it fixed the problem.

Today the scan found the same problem on another random file. What the heck is causing this? What does "invalid context during scan" even mean?

I don't surf any dodgy sites or download shady apps, so a virus seems extremely unlikely.