Well, after working hard with the development team over at Sage, it seems that the issue is with the version of the Amyuni PDF driver that ships with Sage Line 50 2010.
It does not like Windows 7 at all.
The good news is that Sage now know about the problem, and the fix is to upgrade to the latest Amyuni 4.0.9 driver. But there is a problem……
The installer that Sage uses has a special “Sage only” key. That means that unless you are willing to go out and buy the Amyuni driver yourself, you are going to have to wait for Sage to release a PDF driver update patch for Sage 2010. They wont do that unless their support team gets calls about this issue, which of course will not happen until the release of Windows 7 tomorrow!
Keep the pressure on, this is one patch that will be needed! Sooner rather than later.
If you are REALLY stuck, post here, and I may be able to help.