IP lease renewal problem with ISP's DHCP server

[nmutis]

Lately I've been having problems renewing my IP lease from my ISP's DHCP server. The lease itself varies from 15 minutes to 30 minutes each time. Even though that's more than enough time for it to be renewed, during the last couple of days it has been unable to do so many, many times and I'm forced to renew it manually or disconnect the modem.

When I try to renew the IP manually (via ipconfig /renew), I get the following error:

Windows IP Configuration

An error occurred while renewing interface Internet : unable to contact your DHCP server. Request has timed out.

Upon looking at the Event Viewer after I lose the lease, I'm flooded with warnings that all look like this:

Your computer was not able to renew its address from the network (from the DHCP Server) for the Network Card with network address xxxxxxxxxxxx. The following error occurred:
The semaphore timeout period has expired. . Your computer will continue to try and obtain an address on its own from the network address (DHCP) server.

For more information, see Help and Support Center at

http://go.microsoft.com/fwlink/events.asp.

These are followed by an error:

Your computer has lost the lease to its IP address xxx.xxx.xxx.xxx on the Network Card with network address xxxxxxxxxxxx.

For more information, see Help and Support Center at

http://go.microsoft.com/fwlink/events.asp.

What can I do to remedy this? Change my cable modem? Format and reinstall my OS?

Thank you in advance.

P.S.: I’m using Windows XP with SP2 and have Kerio Personal Firewall v2.1.5 installed, with ports 67 and 68 opened for DHCP. I’m also using a 3Com HomeConnect Cable Modem External.

 

[nmutis]

Sorry, I finally found out what it was: NetLimiter was "blocking" the whole renewal issue. I unstalled it and I have not had a single IP lease renewal attempt that has not worked.
Please disregard this thread.