Win XP Laptop can't see Mac OS X 5.8 & Vice Versa

[tallbarb]

Just switched from DSL to Cable modem with an SMC Barricade (SMCWBR14S-N4) router. Ever since, all my network mappings to the Mac on my Laptop don't work and I can't browse to the Mac at all. I can't see the laptop from the Mac nor the Mac from the laptop. If I plug in my old Actiontek router, it works - but of course I have no internet access that way as it is for a DSL connection. I am positive all things that need to be shared are shared and the workgroup names are the same. I can't ping the router or the laptop from the Mac (not permitted). I can ping the router from the laptop but can't ping the Mac. Also - when the Mac is connected to the internet via the SMC router, the connection drops constantly and downloading is so slow I may as well be using dial-up. I think the router is the issue here but how do I know for sure. Has anyone else had this issue?? Any advice you can give would be welcomed. I am ready to call Comcast and tell them what I think.....