VNC 4.0 and 3.8 Connection doesn't always work

[CABNVA@aol.com]

My home computer is connected directly to my Comcast-supplied modem (no  
router) and I have no firewall (I have one, but turned it off to test my  
connection). I have successfully used VNC 4.0 to connect to my work computer as  
recently as 2 weeks ago and can't think of any big changes to my computer since  
then.  Now I cannot connect or receive connections. I had a friend attempt  to 
connect to my work computer from her computer, and she was successful. When  
she tried to connect to my computer at home, and she was not able to  connect 
either. When I try to connect, it times out with an error 10600 or  something. 
I've tried both versions 4.0 and 3.8. My friend successfully used her  
HelpDeskVNC on my computer (I downloaded the application which connected to her  
computer).  I can't figure this problem out. I don't know of anything  that's 
changed. I rebooted my modem and computer. The only thing I can think is  that it 
must be something with Comcast. Any  suggestions?