Hehe..TG for TPTF

try running nslookups from the command prompt on the domains you can't reach. Could be a lot of things, but the nslookup rules out dns with your provider. If you can run nslookups, run a tracert from the command line to the domain/IP in question.

Here is an example:

C:\Documents and Settings\>nslookup plantedtank.n
et
Server: ns1.appsitehosting.com
Address: 209.196.22.10

Non-authoritative answer:
Name: plantedtank.net
Address: 65.61.185.19

C:\Documents and Settings\tracert 65.61.185.19
Tracing route to 65.61.185.19 over a maximum of 30 hops
1 <1 ms <1 ms <1 ms 10.10.0.225
2 54 ms 55 ms 53 ms 65.14.248.7
3 54 ms 55 ms 55 ms 65.14.249.93
4 55 ms 54 ms 55 ms 205.152.208.12
5 56 ms 55 ms 58 ms axr01asm-so-0-1-0.bellsouth.net [65.83.238.41]
6 54 ms 111 ms 56 ms AXR00AEP-0-1-0.bellsouth.net [65.83.236.50]
7 56 ms 55 ms 57 ms 192.205.34.189
8 82 ms 82 ms 83 ms tbr2.attga.ip.att.net [12.122.96.82]
9 89 ms 91 ms 77 ms tbr1.dlstx.ip.att.net [12.122.2.89]
10 76 ms 79 ms 76 ms tbr2.hs1tx.ip.att.net [12.122.10.130]
11 76 ms 76 ms 77 ms 12.122.103.65
12 86 ms 85 ms 85 ms 12.87.122.246
13 83 ms 80 ms 80 ms vl130.core1.sat.rackspace.com [64.39.2.33]
14 85 ms 86 ms 87 ms vlan907.aggr7.sat.rackspace.com [64.39.2.218]
15 81 ms 80 ms 80 ms 65.61.185.19

If you see where there is a * * * for one or more hops, there might be a problem with the route between you and the target server. If you see this for a lot of different domains that you frequent, then it is probably safe to say that there is a routing problem between you and a portion of the Internet. Many times this happens when there is a train that derails somewhere or something else of that nature. Fiber trunks are run right next to train tracks because the land has already been cleared. If a train derails, it is bad news for the fiber that is right next to the tracks. It has been known to shatter for miles away from the wreck.

Usually routing problems are fixed within 12 or so hours or less, so if thats the cause you should be back up by this evening.