I see these as key points:
- Also attached to the router is a fileserver.
- Mapping of a shared drive on the fileserver from windows xp times out
The file server looks like it is not configured appropriately.
Other things you say regarding the Linux boxes point to samba on openSUSE being correctly configured, so at this stage I recommend that you don’t fix it (because it’s probably not broken).
So then, about the “file server”: Is it a USB drive attached to a port on the router and shered from the Linux code in the router? Is it a computer attached by wireless or ethernet wire to the router? Is it a NAS box attached to the router? Please describe the “file server” in terms of its physical nature, how it connects to the router and how it is configured to share “drives”, including if it has an operating system and if it does, what form of networking is used therein.