Actually, I misspoke. It may not be illegal to discuss (depending on whether signed NDAs have laws to back them up in a given jurisdiction), but it would certainly get your seed key revoked if Apple found out.
Sure, Apple can revoke your seed key whenever and for whatever reason they want.
The existence itself is public, yes, but historically, many things have been covered by the NDA for a given release. Normally, these include things such as benchmarks, debug files involving OS-level components, feature lists or descriptions, application compatibility, OS compatibility, new or changed APIs ... In short, the NDA normally says you can't discuss anything that Apple has not publicly disclosed, themselves.
Most of that makes sense to me, since it's either wildly subject to change or something that's a possible competitive advantage, but application compatibility is neither. Any update, major or not, can break third-party apps (e.g. 10.4.10, USB, and Fusion), so it's not like there's anything new there. It's advantageous for everyone if bugs can be fixed (or at least be known) before release. General communication with a third-party developer about that developer's products doesn't seem like it should violate the spirit of such an NDA, regardless of the letter.
Apple's legal department may of course not be reasonable, or I might be missing something. Apple can revoke your key regardless. macfoe should probably delete the attachment on the off chance that some sensitive information leaked into it. If other people want to report 10.6 crashes but don't want to use public channels, use the beta bug reporting form or email fusion-feedback.
Note that I do not have a seed key, but I've discussed them with people who do. They could have been lying to me, but I doubt it.
Disclaimer: I don't have a key either (AFAIK) and as always, these opinions are my own. I haven't talked to Legal or anyone else about them.
Edit: Unless the username is fake, I think suggests that talking about Fusion/10.6 compatibility (in general terms at least) is OK 
I've got a similar problem - my VMs will boot, but they are really unstable. Sometimes they will work for hours, sometimes they will kernel error every few minutes after booting up. Happens with XP and Vista VMs - doesn't seem to matter what config the VM has or what else is running in OS X. For me, the the only consistent way I have of reproducing the crash is to try installing a large app, or copy a large file. Even tried creating a new VM with IDE instead of SCSI drives and had exactly the same issue.
Any ideas to try would be most welcome