Pleez help...I have lost file sharing capabilities on my wireless network

Ok... to make a long story short. I have a desktop PC running Win XP Home connected to a cable modem and Linksys wireless router. I also have a HP Pavillion notebook running Win XP Home that connects to the wireless network. Up until last week, I have had no problems connecting to the internet, file sharing, or printer sharing (5months of flawless performance).

As of last week (after I connected to the open network at my school), I can no longer access the desktop from the laptop or vice-versa. Let me clarify. The laptop still connects to the wireless internet with no problems, 100% of the time and stays connected. When I go to "view workgroup computers", each computer can see one another. The problem occurs when I try to open files on either computer from the other. I get the error message: "workgroup" is not accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions. The network path was not found.

At first, I thought my Norton Firewall was tripping on me. So I disabled it, and same problem. Then I uninstalled Norton Internet Security from both computers. Still same problem. I've also disabled Windows Firewall to no avail.

Secondly, I thought the wireless network from school had somehow changed my settings...but everyone I've consulted thus far says that should not be the case.

Now, I don't know what to do. I've changed my workgroup name and double-checked that file sharing is active. Oh...and to compound my dumbfoundedness I did actually connect to my desktop today and opened files...but that only lasted for like 2 minutes before it couldn't open the desktop files any more. But, it still "sees" the desktop....

please help me someone out there. I know you feel my pain.

Thanx

 

with that being said (and I've heard XP Professional is better, but nobody could tell me why), am I looking for trouble if I upgrade to XP Professional. Will all of my software work the same, and will I keep the same settings?