HOUSTON  -  A virus is playing havoc with the municipal court operations in Houston. The court system had to close down Friday afternoon after a computer virus affected staff members' access to data on court cases. Courtroom operations aren't expected to be back in business before Thursday morning. Meanwhile, people can pay fines and conduct other court business, but judges will not call dockets. People who had court dates for their misdemeanor cases will be notified by mail of their new dates. The city of Houston is paying $25,000 to a private firm to fix the virus isolated to 475 of the city's 16,000 computers. City officials identified the problem as a new variant of the computer virus known as Virut. The variant infecting the city's computers - W32/Virut.n - was discovered on Feb. 3, Gwendolyn Goins, spokeswoman for the municipal courts system, said in a story for Monday's online edition of the Houston Chronicle. The virus infects winlogon.exe, the part of Microsoft Windows that handles the login process. City officials said the virus was preventing them from logging into the system and accessing information.