I booted up my laptop today (having the 6/29 definitions). You guess it, this happened to me too.
Just wanted to provide some additional information. My program was 7.0.1426 / with 6.29 definitions.
I went to the Virus vault, after reading this message thread, validating the false positive. I right click on the file, but the restore option was grey'ed out, so there was no way to restore it from my virus valt. The only option available to me was right click, then extract, which I did, to the desktop. I then copy the file and put a copy into the right place ( c:\windows\system32\drivers ).
I just wanted to post the my own file checksums for those of you either thinking of downloading it from the net (because you lost the file because Avast program deleted it) and cannot recover it. I am posting these file checksums, so others who has the legitimate file, or Avast people can corroborate their appropriate file checksum for the legit file. It is best if you can "extract it" and put it back to the original spot. I am making this post, because the "Restore" option was grey'ed out, and let's say I felt quite hot under the collar for quite a while, until I found the "Extract" option.
File: cercsr6.sys [File version 4.1.0.7405] File size: (39,904 bytes)
CRC-32: 2e7c29d4
MD4: 484dd71d8a5a9879ba8744655e4b7cc6
MD5: 84853b3fd012251690570e9e7e43343f
SHA-1: 14095c2bb0d6d5ca3310b36bb6be2d657d1d0a0d