OK, this has been a three day journey that I thought ended happily, but....
To make a long story short, deleting a program from the server caused a registry hive error. Fixing that caused an lsass.exe error. Either way, I couldn't boot into the OS. I installed SBS on another drive and was able to access a backup. Given the error seemed to be coming from the System32\Config folder, I just overwrote the Config folder with my backup. Everything was perfect then. I then deleted the temporary OS and formatted that partition.
The server is the DHCP, and it is giving out IP addresses and DNS and such to all the clients. They are able to obtain Sharepoint and access the Internet. All of them can ping the server. But, they can't access any files from the server. They always get the don't have permission error.
They all seem to be on the domain when you look at their computer name and with the other things they can do.
I am not sure if this is an Active Directory issue or DNS or what.