The function SysQueryClassList does not work after resetting the WPS (with RESETWPS.EXE from WPTOOLS, for example).
A possible workaround for this problem is to open a new OS/2 session and issue the SysQueryClassList from within this session. This workaround may not be effective in every situation.
This bug seems to be fixed in WARP 4.
Source: Christian Langanke (see EMail Addresses)