I'm on a Nexus One with Android 2.3.7 (CyanogenMod-7.2.0-passion), and recently I've noticed some sent messages go into the wrong contact's conversation: I send a message to person ABC, the person does receive it correctly, but when I check later the app shows it as sent to a different person XYZ. This really messes up the conversation and gets confusing quickly.
This has happened thrice so far, and there doesn't seem to be any pattern to it except both the contacts involved were people I had been messaging recently at those times. Note that the correct contact does receive the message, it's only on the display of the Sent message that this bug happens.
I'm using Handcent app, but the same display issue occurs in the default Messaging app. In both cases, the message details that comes up after a long press on the message shows the correct number. But somehow, it is still shown under the wrong contact. I've also tried restarting the phone, doesn't help.
Edit: I checked them all, and there does seem to be a pattern here - in each case, if a message ("msg1") sent to A is wrongly displayed under B, it turns out that B was the person I sent the next SMS after "msg1". That is, I send "msg1" to A, then after some time (varies from a few hours to a few days) I send a different message ("msg2") to B, "msg1" and "msg2" both end up under contact B one after the other