What version are you using, have you made any specific extension?
We have found that mysql accounts for about 3% of the system activity, so it should not cuase this problem. Ask you ISP for statistics as the what exactly is going worng.
Some advice
1. Use persistant database connection
2. php accelerators will help, but it depends if your host will let you run then. Are you shared, CoLo, managed? 3. Add indexes to mySQL maybe they are missing
I hope this helps
Tony
Tony Wood : twitter.com/tonywood
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Experts in eZ Publish consulting & development