I installed the latest unity editor last night (4.6.2), and avast hit on the interpreter executable with a “FileRepMalware” alert.
File "C:\Program Files (x86)\Unity\Editor\4.6.2\Data\Mono\bin\mono.exe" is infected by "FileRepMalware" virus. "File System Shield" task used Version of current VPS file is 150201-1, 02/01/2015
The file was also instantly deleted, rendering the editor completely useless.