Is my router my problem?

Folks,

My trusty Netgear DG814 has served me well but I'm worndering whether it is now starting to show its age.....

Setup
DG814, latest 4.10 firmware from netgear website connected to a single PC running XP Media Centre which in turn is running McAfee Personal Firewall Plus. Router and firewall configured for Port Forwarding on 1 port for P2P software.


Symptoms
Unable to get consistent +ve TCP / UDP tests on a P2P test website - usually both firewall and the prognosis is router / firewall settings. Have tried totally disabling firewall to rule it out but the results are the same
Intermittently, I'm unable to access my router via IE and http://192.168.0.1. Sometimes I don't even get to the login screen, sometimes I login in and then it immediately causes IE to "unable to display webpage", or it lets me in to the basic settings page and then bombs out when I try to navigate between screens within the router.
Occasional poor download speeds on http and/or intermittent website access problems (I usually blame the ISP here)

I'm not sure if the problem gets worse if I open the P2P software - it feels like it does. I'm wondering if the P2P software is hogging all the bandwidth / connections between the PC and the router. Any thoughts as to the max connections a DG814 can handle (I've not applied any fixes to the registry to overcome XP SP2 connection constraints).

Any thoughts?

I'm no expert although I am quickly learning.

Thanks in advance for taking the time to read this, and many more thanks if you can help

Regards