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I only tested Vista briefly but I noticed several bugs remain unfixed - in fact I only noticed one improvement!
apart from expiration of Remote Desktop in beta version
The Release Notes for Windows XP Service Pack 3 [download.microsoft.com] documents a workaround to remove the test certificate that is responsible for the text message being displayed.
I'm not certain if that is the issue you are describing, but perhaps worth a look.
[edited by: tedster at 9:25 pm (utc) on Aug. 31, 2008]
[edit reason] removed business specifics [/edit]