LAN/WAN issues and general confusion, help!!

I look after a network that has two separate locations.

Location A
Home of the Domain Controller, active directory and terminal server.
192.168.0.x local IP addresses, issued by the DC

Location B
Small file server, local users who also connect to terminal services.
192.168.1.x local IP addresses, issued by the Router (MikroTik)

Both A and B have identical MikroTik Routers which each have their own IP and establish a link between the two premises. All servers run Windows Server 2003 Std and all PC's are XP Professional SP3

Issues
At location B despite the router being setup to issue the same IP address to each machine based on the man address the machines seem to be "forgetting" their IP addresses. Nobody realises until they check their mail. They run ipconfig /release then .../renew and all is good, maybe for a couple of hours maybe for a couple of days.

At location A no forgetting of IP addresses but the network performance is definitely down, malware scans came back clear across the board. The most recent symptom is a networked HP printer that had its jetdirect card replaced now takes up to 10 minutes to print a test page. Uninstalled and reinstalled with new driver files and everything but no change. Then some afternoons it will run fine.