[plt-scheme] collection not found error at startup

Hi,

I am using the debian package of mzscheme.  Recently (must have been
after an upgrade), it started giving me this error message at startup:

Welcome to MzScheme v4.0.1 [cgc], Copyright (c) 2004-2008 PLT Scheme Inc.
lib: standard-module-name-resolver: collection not found: "scheme" in any of: (#<path:/home/tpapp/.plt-scheme/4.0.1/collects> #<path:/usr/lib/plt/collects>) in: (lib "scheme/init")
standard-module-name-resolver: collection not found: "scheme" in any of: (#<path:/home/tpapp/.plt-scheme/4.0.1/collects> #<path:/usr/lib/plt/collects>)

Any ideas how to fix this?

Thanks,

Tamas