I would suggest rather then simply removing either version of AVG to simply disable it in the msconfig utility for the time being until Grisoft sees that corrected. For the 8.0 only one item is seen in the startup tab while the two email scanner and Watchdog items are found in the services tab on both XP and Vista alike.
First check off the "hide all microsoft services" box to avoid inadvertently disabling any necessary MS background services by accident if you are new to the utility included in Windows as a diagnostics tool.