samba - Jul 2010 - i/o error

I am trying to mount a share from samba 3.0.34 server and am getting the
following error:

---
 mount -t cifs -o username=ppradhan at mydomain.edu //x.x.5.197/ppradhan /mnt/
Password:
mount error(5): Input/output error
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)
---

however, if I use windows XP machine to mount the share I can do it without
any problem but can't do it my linux and macosx client using CLI

Any ideas?

Thanks!
Paras.