MSN-specific connection problems

"Retrieving Contact List 100%" / "Reading error"

This is caused by "incorrect" contacts in the contact list. If you're running into this error you need you need to remove the offending contact. You can identify it by getting a debug log (see CurrentAdiumDebug for instructions) and looking for the following sequence in the log:

(Libpurple: msn) FQY error 241
(Libpurple: msn) FQY response says 
<offending contact> is from network 0
(Libpurple: msn) Ignoring user <offending contact>
about which server knows nothing.

If removing the contact doesn't work with Adium, you could try with the original/mainline client. #p10023 has details.

"Unable to add user (Unknown error 204)"

This can happen when with certain Yahoo users on your MSN contact list. The workaround for "Retrieving Contact List 100%" / "Reading error" also applies here. #p8988 has details.

"A message may not have been sent; a timeout occurred"

The bug that caused this problem on some network configurations is fixed in Adium 1.4 but this error can still happen if you or the person you are talking to are having real network problems.

"Message could not be sent because the user is offline"

(even though the user is online)

This is related to the the problem above and happens on some network configurations. #p10049 has more information.

"Buddy list synchronization" error

This Pidgin Wiki page has information which helps you to solve this issue.