ODBC (again)

I use NAV W2.6, native db on 2k3 Windows server. All of a sudden I cannot connect (through ODBC) to my Customer table anymore, neither in MSAccess nor in Excel. My CPU goes beserk if I try to. I can connect to any other file in the db. I checked for viruses, kicked everybody out of the system, restarted everything, did the Navision database maintenance steps,etc. ,nothing works. I have no problems in Navision accessing the Customer table. Can anybody think of a reason ? Thanks