I just read that there is a fix for Sitecore 6 and the .NET framework 3.5 Service Pack 1. Due to this post the Sitecore CMSÂ 6.0.0 Update rev.080820 is released.
Fixed: stability issues occurred with .NET 3.5 SP1 installed.
Fixed: items in a workflow were not automatically versioned when users edited them in the Page Editor mode.
Fixed: the media cache grew even when the link to a media library entry had the same query string parameters as the previous one.
Fixed: in some cases, deadlocks could occur during the recycling/restoring of items.
Fixed: Sitecore CMS could hang if the â€˜Subitems Sortingâ€™ definition in the Type field referred to a non-existent class or .dll file.
The performance of the ItemSerializer was increased.
The SQL generated for fast query can now be customized when implementing new data providers.