I have a similar problem: I'm using AdiumX 0.75.1 to talk to a friend who's using MSN 6.2 (WinXP). Some sentences this friend writes never make it to me!
Until now I couldn't narrow it down to a specific situation, but I found out that every now and then a line of text just vanishes. Neither he nor me get a error message though.
I *THINK* I always see the symbol that this friend is "typing", but then no text showns up. Until now I don't think a line that I sent got lost, but I will have an eye on that and report back.
Anything I can do to help narrowing this thing down?
When you're talking to your friend, make it a rule to type a number before each message like:
You: 0 Hey man what's up?
Him: 0 Not much you?
You: 1 Nothing, just hanging out.
You: 2 You want to have lunch later?
if you ever see a message out of sequence, ask him if he sent one before it .. it's not the most scientific manner, but it works - we had/have to do this all the time when using Y! msg'er because of it's horrible message handling.