FYI: unknown virus TROJAN_MSCACHE.A

One of our customers is infected with a virus that I have yet to find any information: TROJAN_MSCACHE.A. Infects hidden type files in folder C:\WINDOWS\SYSTEM. She has Win98 but confirmed antivirus has latest engine and pattern files. It seems to have affected her Excel shortcut icons that don’t respond but files can be opened from program although she says some look slightly different (no macros involved). She then loses the programs running in the background until she freezes. Searched antivirus websites: no information. Alerted our antivirus software company and waiting for any information they might have.
Wondering if anyone might be detecting same virus.