As many SVS\SWV packagers can tell you Office 2007 can require some effort to Virtualize and on Vista there's more work to be done. One error that's confusing is: "This document could not be registered. It will not be possible to create links from other documents to this document." and while it appears mostly on Vista you can run into it on Windows XP. The root cause is what Fonts you have in the base or in the layer just like the "There is insufficient memory or disk space. Word cannot display the requested font" errors you see, which is more common and both of which are more prevalent in SWV then SVS.
Why? Well with SWV we fixed the font loading issues so fonts now correctly load on a layer activate or when set to Activate On System Startup, which means no more having to copy fonts out of a layer to use them--however this lead to an interesting scenario that leads to these error messages which is when you have the same font in the base and the layer yet they're different versions, and different sizes, bad things happen. This is something we plan on fixing, but it didn't make it into the release of SWV 6.1
On our test systems, with default Office 2007 Enterprise install and default Vista Ultimate install, we noticed that removing these three fonts (from either the base or layer) resolve both error messages: Calibri, Cambria and Consolas--however that doesn't mean in every instance removing these fonts will resolve the issue, it just depends on what you have installed.
So even though fonts now get loaded properly it's still a good idea to run copyfonts on layers with lots of fonts, especially when you get font related errors or strange error messages you can't find the source for.