Well, it is working now!
I reset the Wireless router and it fixed (!) the problem.
I still do not understand what was casing the problem though.
I had 1 Windows Server 2008 wirh AD.
1 Laptop #1 with Windows 7 (Wireless) for 4 months (Upgraded from Vista)
1 Laptop #2 with Vista Business (Wireless)
1 Laptop with XP SP3 (Wireless)
1 Desktop with Vista Ultimate (Wireless)
All PCs are in the domain, using a single userID with Administrators Rights.
Since I upgraded the Laptop #1 to Windows 7, I found that once in a while, my Vista laptop would not connect to the wireless after rebooting and I needed to reset the wireless router. XP and Windows 7 where not having any problems, just the Vista (Both Laptop #2 and the Desktop)
After resetting the wireless,I was not having any problems sharing files between Windows 7, XP and Vista.
Yesterday, I updated Laptop #2 to Windows 7. After that, I could not connect to the Windows 7's Laptops, Vista, and XP, but could from the Server.
I reset the Wireless router and it is all working.
Anyone had simular experience with Wireless and Windows 7.
My wireless Firewall Router is a Fortinet WIFI60B.
Thanks for stopping by and for your input if any.