We had 2 Cisco RV042's with a site to site VPN setup. Everything was working great. One of the Cisco's were swapped out with a Sonicwall TZ series with default MTU settings. The VPN works. The XP and only XP users have an issue accessing the file share over the VPN. If I even open "My Computer" and the S: drive is listed, it freezes everything up. If I use command prompt to unmap the drive, then it's fine, but then I have no access to the share obviously. I've changed the MTU in the registry on the XP machines and for most it seems to be working ok. I have 1 user that it still does not work for, but I've verified that the MTU is at 1500. How can I troubleshoot this? There are no managed switches, just the endpoints mentioned above.