Based on what I have seen happen on SS60, it seems to me that the problem is database related. That could be anything from a fragmented index to drive problems to network congestion on the internal LAN between the game server(s) and the database server(s).
Blaming the customer is not going to fix the issue. Sarcastic responses to customers that are having problems and are very frustrated at the lack of attention vs. what the problem deserves is not going to be helpful either.
Suggestion to the company: If you lack the expertise in-house to work on the problem, consider contacting members of a Distributed Computing project. They have to deal with these kinds of large database / high performance situations, so they may be able to offer advice.

