I have exactly the same problem.
And it started sometime after installing the ServicePack1 - but not immediately. Only when I reverted to another system restore point, made a month AFTER I installed SP1, the problem appeared.
I couldn't believe Microsoft could let through such an obvious problem slip through the SP testing, so I tried every other possible solution (including deleting the contents of LogFiles folder), but nothing worked.
Then I restored the system to the point BEFORE I installed SP1 and RAS miraculously started again.
After reinstalling SP1, the problems returned.
Did some additional checking and I'm nearly 100% sure now, the problem is related to permissions (which the installation changed). Alas, I have not been able to identify exactly permissions for which files/devices/registry entries get screwed.
Would greatly appreciate any hints about it.
For now, I'll revert to the pre-SP1 Windows 7, as I really can't afford to lose the VPN connectivity.
what should I do? I don't have the original CD which I used to install my system, can I download another one and then do an upgrade? it seems to help some of the users, is there another quick fix?
If you have an early enough system restore point, you might trying to restore to that point.
However, as I mentioned, restoring to a point AFTER SP1 was installed, actually caused the problem in the first place!
I believe "upgrading" to a clean Win7 version with the install DVD should do the trick as well. AFAIK it doesn't has to be the same DVD you used for original installation, but you have to use the same registration code, as the first time, in order to avoid additional problems.