Wan DHCP

Good day,
 
I am using m0n0 1.3b since about 7 month without any problem's. I have a
cable modem (CTV).
 
Now I have one with the WAN. I am running the WAN in DHCP an I always
get the IP 192.168.2.42 assigned by my ISP.
 
Suddenly I do not get any IP from my ISP anymore. Only the DNS is
getting assigned.
 
I followed according to the handbook trouble- shooting chapter 17.5.2.1
which did not any good.
 
Any way I thought my ISP is having a problem, bud first I tried with my
old router (D-link), and surplice, this on is working fine. The only
difference is I am getting now the IP 192.168.2.116 assigned by the ISP.
 
Now I am pretty much convicted, that the problem is on my side (m0m0). 
 
Has any one a idea what the problem could be?
 
 
Thank's for your reply
 
Best Regards
 
Andy