I just tried using different orders of the parameters in the mount command and also the parameter "user=" and "username=" . Neither makes a difference on my N800 OS4-2007.26.8, it works here.
I think the smbmount requires "username=". Also using smbmount - in case it is available - gives more verbose output than mount. BUT: smbmount mounts smbfs-type shares. This is basically equal to cifs, but a kernel using only the cifs.ko knows only about cifs-type filesystem and smbmount will fail. The filesystems known to the kernel may be listed using

cat /proc/filesystems

I am mounting "local" shares, ie. no firewall in the way, the same network segment.
I would also try mounting using the IP-address not the Windows server name.:

mount .... //192.168.1.3/share /mount-point not
mount ... //server-name/share /mount-point

This removes one tricky point: windows name resolution.
In case you are using a linux samba server, you may check the messages on the server (not the N800 client) while trying to mount: either

tail -f /var/log/messages or
tail -f /var/log/samba/log.smbd.

These filenames are valid on my debian, but these are quite standard. The second source is more verbose.

Good luck.