Hello, from what I have read on line, your router has issues dealing with certain Linux kernels; you can try to install the latest firmware and see if it helps, otherwise I fear you may need to simply retire your beloved router and buy a newer one. Unfortunately I did not find this router on the supported list for dd-wrt so that would not be an alternative solution. Maybe someone else has better info. Good luck.
Regards
The Cleaver
Regards
The Cleaver