It looks like avast is alerting on Panda's unencrypted signatures or something along those lines.
Personally I wouldn't have Panda on my system, even if it is an on-demand scan. If it is anything like its on-line scanner it installs its unencrypted virus signature files in a sub-folder of the c:\windows\system32 folder. I think that is taking liberties doing that in the system32 folder, not to mention these unencrypted signatures are going to be detected by avast (or any other antivirus installed) when you scan that area and the system32 being an important system folder is going to be scanned by all scans.
Personally I would recommend uninstalling Panda's Activescan.
The avast Win32:Malware-gen is a generic signature (the -gen at the end of the malware name), so that is trying to catch multiple variants of the same type of malware. So seeing other avast users with this detection is not unusual.