Could be to do with the installed service packs.
.Net Framework Version 2.0 with Service Pack 2 is the latest version, and fixes all sorts of stuff. It Requires Windows 2000 SP4 on Windows 2000 plus the
KB835732[
^] or
KB891861[
^] updates.
Even with all this installed there may still be problems according to Microsoft.
In addition I would recommend your client upgrade. Even the
extended support[
^] for Windows 2000 ends 13/07/2010.