Various Things Lock Up After A Variable Amount Of Time

Not very descriptive, but so the computer goes. Lets say I am updating a blog. And I refresh a number of times, once for each post. Not always the same amount of refreshes, but eventually I get the spinner upper right, and the status bar says either 'Done' or 'Stopped'. If I check email, first time fine. I close email. Over the next 2-5 hours, I open email again, close again, open again, Mozilla Thunderbird newest version, and it says cannot connect. The number of times it will work and then stop, varies. To fix either, I reboot, no need to do anything else, and they work fine again. I get the impression that if I have to connect to anything outside my home computer, this occurs. I haven't tried all software, but it happens with email, both browsers, and connecting to Everquest. So it isn't just one type of site/server. Just anything outside my home computer. I'm the only user and admin.