version GLIBC_PRIVATE not defined in file libc.so.6 with link time reference

[Rob Gom <rgom.debian@gmail.com>]

Hello,
I have updated my PC from i686 to Intel Quad. Therefore I switched to
64 bit kernel. In the meantime I upgraded my libc from 2.7-something
to 2.9-23.
After that smb:// protocol no longer works in KDE3 (yes, I have
decided to stay with that version - it's fine for my purposes). Log
message is:
Could not open library '/usr/lib/kde3/kio_smb.la'.
/lib/i686/cmov/libnsl.so.1: symbol __libc_clntudp_bufcreate, version
GLIBC_PRIVATE not defined in file libc.so.6 with link time reference

What can I do with that? Does it seem to be a KDE3 bug or libc6 bug?
I searched google but with no useful results.

System: mainly SID (mixed with stable & others)
Kernel: 2.6.30-amd64

Regards,
Robert