I would look to DNS problems. If you are on a Mac it is common for them to have such problems. On a Windows system it tends to be more of an ISP problem.
I see lots of this in Second Life. Enough so that I wrote up
Troubleshoot your SL Connection. Whether it is a web site, Uru, or SL you are having problems connecting to the steps in the article will help you find the problem. Of course the SL specific stuff is meaningless for your use.
If you are on Windows, you could write IP addresses in for the MOUL forum and other sites you have problems with into the HOSTS file. If it is a DNS problem in your computer or from your ISP, that should fix it. Of course if they change addresses at some point you won't be able to get to the sites and remembering that you have HOSTS changes is not likely. So, it can be a gotcha at some point.
If you leave the computer on 24x7, you might try clearing your DNS cache.
If you suspect an ISP problem, switch to Google DNS servers. Google has good instructions on how to do that. They have left out the advice to keep at least one of your ISP's DNS servers in your settings. Some ISP's have special values in their DNS for mail servers and support services for their subscribers.
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Nalates - GoC - 418 - MOULagain: Nal KI#00 083 543, Nalates 111451 - Second Life: Nalates Urriah
Guild of Cartographers 