Yes, be aware of this...
V-Vocal is basically a plugin and was removed in X3 (and replaced as the Sonar included pitch correction tool by Melodyne). Normally (I believe but am not sure because I've never removed anything) if you had missing plugs in the FX Bin/Rack you'd get a "Missing Plugin" dialog. Likely the fact it's a "Region FX" is what's causing the issue (the clip is seeking out V-Vocal and can't find it thus bad things happen). I'd expect similar issues with open Melodyne, V-Vocal, Audiosnap, etc tools.
1) Best to bounce Region FX anyway (like do your work and bounce the bugger... you can always reopen and edit the "Region" afterward or, if you made sure to keep a copy of the original clip, start from scratch... I always make copies and edit the copy instead of the original).
2) I'd have to check my account but if you bought your upgrade to X2 in the Cake store the whole package should still be available. It might be separated from the main CCC store stuff though. My pre X3 downloads appear like they used to (IIRC) and then the new store stuff is all displayed/accessed in the new format. I am an "offline" installer though so I can't speak to what appears in that installer app as far as old downloads.
If you paid for the version and have all the s/n's and reg codes but do NOT see those downloads just contact Cakewalk and they should provide new links/fix your account.
The only time a purchase would be missing would be the FIRST boxed purchase (from the olden days of physical media) but even then I think Cakewalk provides online downloads in the case someone loses their discs (eg: I bought boxed X1 Production Suite as my intro product. If I lost the discs and wanted to install X1 I think I'd be able to get a downloadable version of the entire package... I THINK).
So yeah...
Always bounce Region FX ASAP and if you aren't seeing a registered product in your store page contact support to get it sorted out.
It should also be noted that when they updated the store/forum site with the SSO stuff (right before X3 IIRC) they asked everyone to double check their accounts to make sure all their products were still in there. You may have had your X2 upgrade/downloads hoovered up during the switch... which can be remedied.
Cheers.