hmm, well this wont really fix your problem but it will at least tell you if the WAN is reachable etc and perhaps look elsewere for the problem..
there are many ways you could do these tests but the fact you seem to have another working web connection else you couldnt post here, heres what id do.
first of all ,double check the obvious, has VM accounts messed up and wrongly turned off your CM access?,they have done this to me several times so its quite possible, you can still ping websites using the internal vm DNS servers etc, but not go any were when they wongly do that.
'Network Access : Allowed' in
http://192.168.100.1/CmOpConfig.asp if they havnt turned you off.
as already said, lots of ways to quicky check, but use your working connection to check the current broken VM WAN by making a quick shell account here, just follow the on screen text.
http://sdf-eu.org/index.cgi?telnet and ping (and other shell based things)your routers WAN IP directly from that external shell account, when your connected to that crumby flickery java web front end your in effect external to any VM part so even if your connection your using to post now is also another VM conection it doesnt matter.
you can use putty in the java front ends place, but its just a quick test so the web java front ends fine for that.
your installed OS is probably fine,but again, as a quick check go grab any of the slax liveCD's and boot the PC on your LAN to see if it can now get a valid LAN IP and browse the web.
http://www.slax.org/download.php
any will do,
SLAX Standard Edition v 5.1.8.1 should be fine for a test if you have an average bog standard PC/NC as must people do today.
useing these liveCD's does not write anything to your Harddrives etc (unless you tel it to OC)so no problem, just a nice quick way to see if the OS<>PC<>router<>CM<>VM-network<>web is now working.
if it is, then its time to look at the HD installed OS etc.
other than that,im out of idea's for now, and times moving on, things to do and all that..., hope at least some of this helps a reader or two to at least diagnose and perhaps fix a/the problem their end.