certain sites unaccessable

The internet connection at my work has been acting very strange for quite some time now. When I try to access certain sites like hotmail, newegg, and many others it will just hang and say "waiting for
www. .com" It will do this for a few weeks, then out of the blue i will be able to access all these sites. Then after a couple weeks it all starts over. There are 3 computers in the office which are all connected to a linksys router on DSL. This behavior is happening on all 3 computers. I checked the router config and there were no restricted websites. I talked to SBC/yahoo support who walked me through a bunch of obvious crap and who also said they have no restrictions set, so we should be able to access everything. I have no clue what is going on.  
abmacomberAsked:
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IanThCommented:
try doing on one pc

run / cmd

ipconfig /flushdns and then restart as it could be virus's or spam affecting your local resolver cache

if that works then scan all your pc's with an up to date virus defence package and then do the above on all your pc's
gkumaranCommented:
Check for the WAN IP address of the Linksys Router, some times it may get a Private IP address as WAN IP. This means that there was already a Router in place, creating a double NAT.

Note: Private IP is any IP address in following range
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
sappsysCommented:
I found a similar problem with a friends router. He would have a bunch of sited (ebay / banking etc) that would stop working, then would start again. We spent ages playing with DNS etc to try and diagnose it. We finally ended up tuning his MTU (maximum transmission unit) value to be a bit smaller 1492 instead of 1500, this fixed the issue.
You shouldn't have to do this, but it worked for us.
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x_X_x_X_xCommented:
Yeah I agree with sappsys this sounds like the MTU settings you can go to dslreports.com and they have allot of information regarding MTU settings as well as ping test you can perform.....Also I would see about a firmware upgrade for the router if the ping test passes.
Hope this helps...

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abmacomberAuthor Commented:
Well I am now checking this site from work...a site that was previously not working.  thanks everyone!
abmacomberAuthor Commented:
Oh yea... it was the firmware upgrade that did it
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