Tab completion breaks after upgrade

[lists <lists@xxxxxxxxxxxxxxxx>]

Hello all,
	It's been my experience on several different machines that when I 
upgrade the version of zsh I'm using, tab completion stops working.  
This happened going from 4.0.6 to 4.1 and again when I moved to 4.2.  
When I type the first part of a command and press the tab key (in this 
case the 'pri' in 'print'), I get something like the following:

% pri_alternative:69: command not found: _suffix_alias_files
nt

I get around the issue by backing up ~/.zshrc, then running compinstall 
again, and replacing my original ~/.zshrc file for the new one 
generated by compinstall.  Does anyone have any ideas?

Thanks!

P.S. I didn't include my .zshrc file because it's quite large an messy 
but will happily do so if that would help.