The 404 errors you first reported could be related to mod_security
It’s a bug in MySQL, period. There are many posts about it here, WordPress had to modify their code to work around it, but the ORDER BY failing when a GROUP BY is used is the problem and it is definitely MySQL 5.0.51; there is more discussion here and here.
My host, directNic, looked into it further and fessed up to the fact that they are using MYSQL 5.0.51. Thanks for giving me the confidence to push back. Unfortunately they said that it was MODx that was the problem, not MYSQL. Are there any posts out there that document the problems with 5.0.51 as being larger than just with MODx that I can point them to?
The 404 errors you first reported could be related to mod_security
Can you be more specific about what the problem is or what I might need to do to fix it?
Thank you!