For some reason, TREMAN (I assume this is what you use) doesn't always work in two cases IIRC:
a) The .TRE is read-only. Open the file properties and uncheck "read-only".
b) Sometimes on win98 I couldn't start it from a directory where in the structure there was a space. IIRC I couldn't reproduce the problem under another windows... go figure. Maybe it was windows that was messed up. It would be safe to use it from a standard 8.3 directory though. Like c:\projects\tre_cont\ for example.