Unity is currently having issues with Avast causing some users to experience getThreadContextfailed errors during gameplay.
Many Unity support members are saying the common issue is using Avast.
I have noticed an issue with this for the past week (loading games directly purchased via an online store.) There is a fix according to the developers which involves the mono.dll being compiled to work around the A/V system. It should be noted that avast has not alerted people to a blocked item during this however its leading to suspicions that since v8.0.1482 there has been problems with Unity and Avast clashing. (People have tried adding the Unity engine to there exclusion list however this has failed to work.)
Just wanted to let you guys know in-case your wondering whats going on or if you wasn’t sure this was a False Positive.
Current post reporting on this issue: http://forum.avast.com/index.php?topic=125583.msg950622#new however it is not being reported as a false positive.