This happens sometimes with large sites running on cost-efficient hosting.
The Pro version of WP Word Count has an incremental word count calculation routine that performs much better than what the free version uses. I plan on implementing that into the free version in a future release.
I do get the same error when trying to deactivate and activate the plugin (to correct the author count, hopefully).
Now, nothing works. Too bad.
Version 3.0 has a new method for initialing calculating your word counts. If you want to give that a shot and let me know if you see improvement I would greatly appreciate it.
Worked like a charm now. Calculating went through without problems and statistics work, too. Thanks for the improvement!