The problem you bring up only applies to Messenger versions 5.0 and above, which use HTTPS services as an authentication component, and this was intended when Messenger was originally operated, but Escargot is a special case, as @valtron didn’t consider HTTPS compatibility with old systems and went with what he felt was the “most secure” for Escargot to work on XP. I go into more detail in a reply to a post concerning the support of MSN 5.0+ on Windows 98:
Also I do feel like Escargot should lay back on the HTTPS a bit. But that’s in edge cases like for the HTTP gateway that isn’t public, but has been developed on for quite some time, and should be considered being used,
As for a solution to your problem, your best bet right now would be patching XP to use the latest root certificates and IE8, but I can assure you that I’ll try to find a way to avoid this complicated compatibility issue. Or you could use 4.7 and below, but you have to make sure you enabled old MSN support on your account before you try to log in.