Any apps that makes a URL connection crashes

Question

Any app that connects to the internet using a url address on my MacPro crashes (Software Update, Safari, iTunes, App Store, etc). I can connect to the other computers on my network normally and have no problem moving files back and forth. I can ping an external IP address, but anything that tries to connect to the internet using a url causes a program crash. My other computers on the network can connect to the internet normally.
In the crash logs there is always a Crashed Thread and lines similar to the following:
0x00007fff854e85d1 +[PKURLConnection sendSynchronousRequest:returningResponse:error:] + 283
31 ...le.SoftwareUpdate.framework 0x00007fff8098aa39 +[SUURLConnection sendSynchronousRequest:returningResponse:error:] + 180
32 ...le.SoftwareUpdate.framework 0x00007fff809826cb +[SUCatalogFetch _fetchDictionaryFromURL:returningError:] + 299
33 ...le.SoftwareUpdate.framework 0x00007fff809823fc +[SUCatalogFetch _fetchAppleCatalogDictionaryReturningError:finalURL:] + 182
34 ...le.SoftwareUpdate.framework 0x00007fff8098232a +[SUCatalogFetch _fetchCatalogDictionaryReturningError:finalURL:isAppleDefault:usingURL:] + 472
35 ...le.SoftwareUpdate.framework 0x00007fff809820f6 -[SUCatalogFetch initWithURL:] + 128
or
27 com.apple.Foundation 0x00007fff866d48bb _NSURLConnectionWillSendRequest + 137
28 com.apple.CFNetwork 0x00007fff86a03845 URLConnectionClient::getRequestForTransmission(_CFURLResponse*, _CFURLRequest const*, __CFError**) + 359
29 com.apple.CFNetwork 0x00007fff86a02b76 URLConnectionClient::clientWillSendRequest(CFURLRequest const*, _CFURLResponse*, URLConnectionClient::ClientConnectionEventQueue*) + 200
30 com.apple.CFNetwork 0x00007fff86a7b952 URLConnectionClient::ClientConnectionEventQueue::processAllEventsAndConsumePayl oad(XConnectionEventInfo<XClientEvent, XClientEventParams>*, long) + 138
It appears that there is some sort or URL connection problem. I've tried repairing permissions, rebuilding the directory, checking the hardware, and rebooting, but none of these have had any effect.
Any suggestions of what to try next would be appreciated.

Answer 1

iTunes & Safari up to date? Have you tried using another browser?
*Disconnect all peripherals from your computer.* Boot from your install disc & run _*Repair Disk*_ from the utility menu. To use the Install Mac OS X disc, insert the disc, and restart your computer while holding down the C key as it starts up.
Select your language.
Once on the desktop, select Utility in the menu bar.
Select *Disk Utility.*
Select the disk or volume in the list of disks and volumes, and then click *First Aid.*
Click _*Repair Disk.*_
Restart your computer when done.
Repair permissions after you reach the desktop-http://docs.info.apple.com/article.html?artnum=25751