Since yesterday's review and the comments I made on Saturday, I'd like to clarify a few things:
MSN Messenger
I don't think the problems have anything to do with the latest version of the MSN client or SP2. Yesterday I was using the same version (6.1.0211) on a Windows 2000 machine with no problems, although this machine did have a much better internet connection than my own computer does. Furthermore, I tried accessing MSN using Miranda IM (new version released on Saturday) and I had the same problem - it was connecting but couldn't retrieve my contact list.
The problem has been intermittent - if I keep trying I do get logged on eventually. I will try again at home in a couple of days where I can also use Trillian, though a quick scan of the Trillian forums didn't bring up any problems. I have a feeling this is because Trillian can remember your contacts, so if it can't get your contact list it can still work.
Performance Issues
The slowdown on startup didn't appear to be an issue this morning - it booted up at the same speed as it always has. So, in short, installing SP2 hasn't impacted computer performance noticably in any way.
McAfee VirusScan
One problem I have encountered is that since installing SP2, McAfee VirusScan hasn't been able to update itself, coming up with an error about the Common Framework Updater system. I'll re-install it to see if it fixes itself.
Update: A re-install didn't fix it. If any of you guys can help me here, I'd appreciate it. The Event Log gives me this message when I try to update:
The application-specific permission settings do not grant Local Activation permission for the COM Server application with CLSID {D3580208-D4E1-46D4-876C-B45A328AF25A} to the user ANNABELLA\Neil SID (S-1-5-21-2402929114-2812750092-2978350642-1005). This security permission can be modified using the Component Services administrative tool.
I'm not currently missing out on any definitions but ideally I'd like this to get fixed. Remember I'm using XP Home, which does have the Component Services tool. It's just that I have no idea how to use it...
Update II: Matthijs, in the comments, offered the solution. Go to Admininstrative Tools and open Component Services. Expand the Component Services branch, then Computers, My Computers, DCOM Config. Right-click on FrameworkService and choose Properties. Click on the Security tab and under 'Launch and Activation Permissions', select 'Use Default'. Click OK, close the Component Services window, and Updates should work again! Thanks a lot Matthijs.
As for Messenger Plus causing the MSN contact list problems, I've never had it on this computer - you can read the reason why here. But this hasn't affected me for a couple of days so maybe it's working again. Still odd that there's no word from Microsoft about this though, it looks like a lot of people are having the same problem as me.