First time I go online for several months, with a new computer, and I get the dreaded "waiting for guest info" followed by "did not receive guest info. Lost connection to host".

LFS is allowed in both directions by my software firewall.
I've rebooted the router.
It's a fresh, full download of LFS S2Y.
On the rare occasion I can connect, pings are good. I don't appear to have a problem with latency or dropped packets on my internet connection. Nothing else I've used my connection for has so much as hiccuped.

Curious things:
- Clicking "back" on the multiplayer screen (going from the screen with options to set skin downloads and browse servserlist or join specific host, going to the LFS main menu) produces a noticeable delay. I don't remember it being like this in the past.
- Going back to the main menu and then back into multiplayer seems to increase the chances of being able to connect.
- Empty servers are easier to connect to than populated servers.

Any ideas? It's driving me up the wall, and given my previous history with a perfectly good connection and no other system issues, it's looking like an LFS-specific issue.

This is getting wierder.

I switched to my test installation of LFS (i.e. version Y14). It was locked, and in demo mode I've just connected to half a dozen demo servers with no problems at all - connected straight away, like it used to.

I unlocked this version of LFS and tried to connect to CTRA1, and failed with the "waiting for guest info" problem. Switched back to demo mode, and now couldn't connect to anything there either.

Are you sure its not CTRA?

Yes I'm sure. CTRA was just an example.

I've switched on network debug in Y14, and when it's waiting for guest info, it's flooding the screen with "UDP: send again".

Now why wouldn't my UDP packets be getting through?

Could be firewall/router port issues. That happened to me when i tried to make a server and the ports wernt fully open.

Quote from mcgas001 :

Could be firewall/router port issues. That happened to me when i tried to make a server and the ports wernt fully open.

Yeh I was going to suggest that too. ESPECIALLY if you have Norton or similar!!! Just for a 5 min test, take down all your firewalls (Windows and the one in your Router) and try it. Post back your result.