Problem creating new users

I’m running the following on my server…

Server Information
Servoy version R2 2.2.4-build 336, repository version 27

JDK Information
java.vm.name=Java HotSpot™ Client VM
java.vm.version=1.5.0_05-b05
java.vm.info=mixed mode, sharing
java.vm.vendor=Sun Microsystems Inc.

Operating System Information
os.name=Windows 2000
os.version=5.0
os.arch=x86

When I try and create a new user via the application server home page, I get the following error…

java.sql.SQLException: [Microsoft][SQLServer 2000 Driver for JDBC]Invalid parameter binding(s). [Microsoft][SQLServer 2000 Driver for JDBC]Invalid parameter binding(s).

When I try and create from within servoy developer, the new user appears to be added by when I login again the user has vanished.

Any Ideas?