SlipperySlope,
You know, man, I've been
waiting for someone to ask this question. I asked the same exact question about 4 months ago when I made the move to DSL. Ah, I'm happy now.
I have a Belkin Surge Master Pro Gold surge protector. My phone line runs from the wall, to the input of the Belkin, from the output of the Belkin, to my DSL modem. I have no problems. I was as paranoid as you are now...w/good reason though. We all want to ensure that everything will run at 100%.
Some questions:
1. Your Belkin prolly has red/green lights that show "good ground" and other status. Is everything OK w/o the phone line plugged in?
2. As Poncherelli said (yeah, we all dug CHIPs when we were younger

) did you accidently plug the line that goes to your Belkin into an in-line DSL filter? If you're using the big old "wall plate" variety, make sure that you have the line to the PC plugged into the appropriate side. It's clearly labeled on the plate itself.
3. Please don't throw rocks, I'm only trying to help. That said, do you have the "input" and "output" line plugged into the correct sockets on the surge protector? Iv'e used Belking products for years and know that the writing on product is small. You really must squint to see it clearly. Double check.
Good luck.
You prolly have a bad phone cable.