Strange internet connection problem

I've had my share of connection problems, but this is something I completely stumped on. I use Firefox as my main browser, but lately when I initially open it, it won't even open my startup page. However, if I open IE it works fine after a slow initial search for my startup page. After IE is open, I can then open Firefox and it works fine until I close it out and try to open it up again. I thought it might be something with the firewall, but Firefox is given full permissions. One other thing I noticed regarding my Motorola SB5101 modem - the LED's lock out no problem when I reset it, but the Send and Receive lights flash 3 times after it goes online. This has never happened until my Firefox problem started. Any feedback would greatly help. And thanks in advance.