CentOS 5 Networking :: Transactions Timeout - Yum / Wget And HTTP

I am having a problem with 5.4 that I did not have with 4.5. The problem happens only sometimes but in specific instances. Basically a summary of the problem is that certain network transactions timeout. The specific instances are with wget, rpm, http. The problem usually, but not always, occurs with pptp stuff. (NOT running pptp but getting pptp stuff). For instance, the following command, which finishes in seconds on non-5.4 OS's:
wget [URL]
downloads about 20% then gets stuck. About 5 minutes later it downloads another 20% and then gets stuck, etc. The same thing with rpm:
rpm -ivh [URL]
waits about 3 minutes and then gives an error. I think it does the same thing as the wget but
wget will keep trying, while rpm gives up. The error from rpm:
Retrieving [URL]
..five minutes later:

I can wget the above as I mentioned before and install it that way. Before I do it, yum works fine. Afterwards, yum exhibits the same behavior of timing out (because it is using the pptp repository). Also visiting the pptp web site from Firefox times out on certain pages. I originally thought it was some problem with the pptp site, but I notice that log into hotmail.com. Does the same thin (fine on other operating systems). A view with Wireshark on the wget (pptp) shows the my machine receiving a reassembled TCPPDU from 216.34.181.96 (Sourceforge), sending an ack, receiving a reassembled PDU, sending an ack, receiving, sending followed by the 5 minutes or whatever of nothing. Then sourceforge sends an RST and a SYN and the process is repeated.

When I put the machine directly on an AT&T IP connection (12.147.X.Y) everything worked fine. Same with Comcast on a direct link. The times I am having problems is when our router is hooked up to a Comcast IP (70.88.X.Y) and assigns 192.168.5.X addresses to our machines. So when I was doing the above from 192.168.5.27 going through the router through Comcast is when I had the problem. So it is probably something with the router, but it is hard to figure out since CentOS 4.5 and Fedora do not exhibit this behavior, nor does 5.4 on most sites (mail.yahoo.com for instance). I did verify, at least from what I could, that ICMP type 3 and 4 are not being blocked. If they were, the same problem would happen on other op systems. And I was able to ping, albeit just locally, but we looked at the router settings and ping was not blocked.