Here is my system's profile as requested:

OS is XP Pro with SP3 installed
Only firewall is Windows version
752 MB RAM
Free space on HD 43+ GB
Cable connection
Motorola SURFboard modem model # SB5101 with Belkin Wireless Cable/DSL Gateway Router model # F5D6231-4
Connecting from house
LimeWire v.4.16.7 Java v.1.6.0_5
ISP is Comcast
Your test worked!
One other PC always connected to network via wireless router. No other PC's running Limewire.
I've been running & sharing files on LimeWire for 4+ years.
Brick wall visible in front of blue world.
UPnP is enabled.
Running Norton System Works 2007 Premier Edition with AntiVirus and Windows Defender. Also run the following free editions on a weekly basis: AVG AntiSpyware 7.5, Ad-Aware 2008, SpyBot Search & Destroy 1.5.2.20 & SpywareBlaster 4.1.0.0
USA

As mentioned above, I've been downloading & sharing music files for a few years through LimeWire. Recently, I updated LW to version 4.18. I am able to connect to LimeWire but unable to download or search for files as I get a message stating that I am not connected to the Internet and to click on Connect in the File menu, which doesn't help. To add insult to injury, although it won't let me search or download any files, I am allowed to sit in front of my monitor and watch numerous hosts upload files from my system even though, "Ahem!", I am not connected. I have tried uninstalling limeWire v. 4.18 & re-installing v. 4.16.7 with no success. I have double checked all browser settings but still have no clue as to why I am supposedly not connected. And since I'm sending this, obviously, I AM connected to the Internet.

I hope I've given all necessary data (it's my first post here) and that somebody can resolve my problem. Thank you in advance for any help you can give me.

SirTom