Dial up problems - me or ISP?

[Ilane Walberg]

Hi,
 
I suddenly started having dial up problems with my ISP.  My configuration has 
not changed and Earthlink claims no changes on their end either (but they 
claimed the same a month or so ago when they added authentication to their mail 
servers and they couldn't tell me how to fix my email because they don't support
Linux!).  Here's what's happening:

I'm running RH 7.3.
  
When I first dial in to the ISP, I can ping earthlink.net (or anywhere else).  
I can pop my email, no problem.  I was able to ftp to my web server and list the 
files there.  But as soon as I try to do certain things, like browse to a web 
page or upload a file with ftp, I hang.  My subsequent ping hangs and I can no 
longer pop my mail.  I did a traceroute and it printed 4 or 5 lines then 
asterisks, but stopped completely when I got the hang. When I hang up and 
redail, I get the same behavior - works with some things then hangs.
 
I don't see anything obvious in the error logs.

Oh, and occasionally, I'll hear a small pop or snap, and my line disconnects completely.
 
Could this be my modem?  Or some new security setting at the ISP?   A combination?  Any thoughts, ideas or suggestions appreciated.
 
Ilane