Avast doesn't seem to be the cause.... It appears the problem has something to do with Spybot. Having said that, it's not that the 2 programs conflict per se.... They get along quite nicely in the notification area..... xD
I have seen the taskbar freeze at the next reboot if TeaTimer is set to startup with the computer when you install AIS. I have no idea what conflicts.
Other freezes: I've found that if I update Spybot (Immunize, for example, or update with the offline definitions file, etc), leave a windows explorer open (My Computer) & reboot, the taskbar will hang. (I have the Restore previous folder windows at logon & the Launch folder windows in a separate process options ticked.) I took off the separate process option & just left the restore folder windows option on, & the taskbar hung as well.
It's an interesting bug.... I know how to avoid the taskbar hang now.... I tested it way more than I care to elaborate.... It was tiring.... xD