If you're trying to patch via logging in to the game client, try this. First, install the expansions (without patching). After making sure your account is active (not frozen) and expansions are installed...go ahead and run the game client and see if it patches then.
I never patch after each install, I always install vanilla WoW and the expansions. It cuts down on install/patching time to let it do one big patch phase. Plus, it may be something bugged in your downloaded version of vanilla that very well may clear up with the installation of the expansions.
If not, I would suggest re-downloading vanilla to make sure you don't have any corrupt files. If patching from a login, I'm pretty sure not having an active account would bug this, because the patching used to kick in after login of an active account.
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