Hello, could be a lot of things, many of them Apple's doings with the OS.
Make a New Location, Using network locations in Mac OS X ...
10.5, 10.6, 10.7 & 10.8…
System Preferences>Network, top of window>Locations>Edit Locations, little plus icon, give it a name.
System Preferences>Network, click on the little gear at the bottom next to the + & - icons, (unlock lock first if locked), choose Set Service Order.
The interface that connects to the Internet should be dragged to the top of the list.
If using Wifi/Airport...
Instead of joining your Network from the list, click the WiFi icon at the top, and click join other network. Fill in everything as needed.
For 10.5/10.6/10.7/10.8, System Preferences>Network, unlock the lock if need be, highlight the Interface you use to connect to Internet, click on the advanced button, click on the DNS tab, click on the little plus icon, then add these numbers...
(There may be better or faster DNS numbers in your area, but these should be a good test).
Thank you for taking time on Thanksgiving to lay out the insructions. We are fortunate for both of us to have laptops so in the morning when I'm more sane and the tryptophan has worn off from all the turkey indulged in, I will give it try. Your instructions make sense on how to find the various steps needed so for this non systems person I should be able to follow you. Operative word is "should." A new post will follow after I try this and will note any error messages more throughly. Something I did not say to begin with was that once the error message showed up tthe machine would stick. Could not do anything like command click Q or restart. Only way to do anything was to turn the machine off manually by hold the start button down for many seconds which is only done in an extreme on that computer. Never seen this before. Looked in recent list also. Hope your day was wonderful. PJH
One way to test is to Safe Boot from the HD, (holding Shift key down at bootup), run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions, Test for problem in Safe Mode...
PS. Safe boot may stay on the gray radian for a long time, let it go, it's trying to repair the Hard Drive
Reboot, test again.
If it only does it in Regular Boot, then it could be some hardware problem like Video card, (Quartz is turned off in Safe Mode), or Airport, or some USB or Firewire device, or 3rd party add-on, Check System Preferences>Accounts (Users & Groups in later OSX versions)>Login Items window to see if it or something relevant is listed.
Check the System Preferences>Other Row, for 3rd party Pref Panes.
Also look in these if they exist, some are invisible...