We got some reports of an issue where using Avira in Windows 7 leads to regular chkdsk-runs upon reboot. Our developers are analysing the problem and now succeeded to reproduce it. We are also in close contact with Microsoft to get to the bottom of this issue. It is not just affecting Avira in Windows 7 though, many other Antivirus products seem to trigger this behavior occasionally too as we learned during the investigation of the problem.
Microsoft introduced a slight change in the NTFS driver in Windows 7. Anyhow, even Microsoft can not pinpoint the problem (which by the way occurs seldom) yet. Update: Meanwhile, we could reproduce the issue and track it down together with Microsoft.
As far as we can tell from the current state of investigation, the problem occurs in special conditions, when an operation is performed upon an already deleted file. This leads to the situation that the NTFS driver / the windows 7 kernel deems the file system as corrupted (which it is not) and sets the dirty-flag of the NTFS partition. This in turn leads to the chkdsk-run on the next start of the system. In previous versions of the windows kernel, the operating system just returned an error.
We found a workaround for this issue. A hotfix is currently being tested and gets hopefully shipped next week as update, if there are no issues showing up in Quality Assurance. The driver avgntflt.sys in version 126.96.36.199 will fix this issue then. We will continue to analyse this issue together with Microsoft as we need to understand the problem correctly in-depth to come up with a better solution; maybe even a Windows Update will be necessary.