I am working on a really bizarre issue that occurred right after I installed SP1 for WSS 3.0 and MOSS. Basically, Export to Spreadsheet works in a regular document library or regular document library webpart, however when I use an XSLT view or create a custom menu item using Sharepoint:ActionsMenu I get an "Unexpected error has occurred. Changes to your data cannot be saved." Every other menu item in XSLT view or on the custom menu works properly. If anyone can shed light on this issue please let me know. I am going to continue to look around for a solution and if I find one I will post it.