Why do I keep receiving IM's even after i sign out of chat?

After I log sign out of chat and shut down messenge, the next time I reopen messenger I have anywheres from 2 to 15 IM"s from ,mainly bots who get ignored promtly, but why do I still receive IM's me even after I have signed out of chat? I know of this hapeening to at least 5 other people as well. This has only started to happen after I upgraded to the new version of yahoo messenger.