This post from Dynamics Confessions blog, informs us about Incompatibility of Dexterity 10.00.320 Build with .NET Framework 3.5SP1.
Those who are working on similar lines, have a look at this article and be informed on what needs to be done in such scenarios.
NOTE: Download Dexterity 10.00.324 Build separately from PartnerSource and install it as soon as you apply GP SP4 on Dexterity. Because this particular Build 324 is the actual SP4 for Dexterity Common Components and Dexterity itself.
Thanks to Mark Polino for his article, which in turn referred to Original Article from Touchstone’s Blog.
POINT TO NOTE: FRx 6.7 SP11 is not available for downloads at the moment. This has been pulled out due to some bug in it. Will be available in another 4 weeks, hopefully.
UPDATE (22nd DEC 2009): We will still be able to download the SP11 but with bug, if I have understood it correctly. I doubled checked it and looks like we are able to download this. But not sure whether the reported critical bug is resolved or not.