I have a wordpress MU database with something like 10,000+ tables for various user's blogs. I need to upgrade wordpress MU to newest version, but want to backup the DB before hand.

PHPMyAdmin fails to even load the page when i click export. Ive tried going into the server (windows) and using dos command line:

mysqldump -u USERNAME -p PASSWORD> BACKUP.sql

but it hangs for a minute and gives me the error:

error 23: out of resources when opinging file '.\USERNAME\wp_1037_links.MYD' (Errorcode: 24) when using LOCK Tables

What am i doing wrong, or should i be doing? Is PHPMyAdmin right for something this size? Is there a better way of doing this than the two methods i tried?

**Note that this is not my site, so any suggestions as to the setup of the DB ill have to run by the owner. Im just here for WP related crap, this is kind of out of scope for what i was brought on to do.