[plt-scheme] Windows + remapped keyboard: DrScheme misinterpreting AltGr characters as commands

Hi,

I use an heavily remapped keyboard (keyboard layout DLL + scan codes
remapped by registry) on Windows, and DrScheme seems to interpret
some AltGr combinations (which send characters) as commands.  For
instance, AltGr + N should be interpreted as _, whilst moves the
cursor or deletes text.

No other application misinterprets those characters.

How can I troubleshoot that? Maybe by tracing incoming keycodes? How?

Software:
- Windows XP SP3
- PLT Scheme 4.2

Thanks in advance