2006 unacceptably slow

I have recently upgraded to 5 user 2006 premier from 5 user 2003 premier. I have upgraded the client on 4 computers and those machines are running ok (a little slower than before, but acceptable). I did a fresh install of 2006 on a brand new P-4 3.2 with a gig of RAM and it is running incredibly slow. It accesses the same data on the server, the machines I upgraded from 2003 take about 5 secondes to open a company, the new machine take about 30 seconds to open the same company. I disabled the firewall, disabled the antivirus on both the client and the server (temporarily) and it had no effect. Everything else on the computer runs great and network speed seems otherwise great. I have re-installed quickbooks once and it had no effect. I then installed QB on my brand new laptop just for testing purposes and it did the same thing, 30 seconds to open a company. It appears that the clients that I upgraded from 2003 are fine, but the fresh installs are not. I restored one of the companies to 2003, and rebuilt the data, then converted it back to 2006, no change. I'm not sure where to go from here, Intuit wasn't much help and I'm almost sure the users will kill me soon.