hmm ok, now that stuffplug lets u see when someone opens a conversation with u, is there a way to block someone with this feature from seeing u when u open a conversation with them?

no, because that's how the protocol work
when you open a conversation, you ask for info about the contact from msn's server, then packets are sent to the other contact from the server

but maybe there's a way to mod msn so that you don't request new info from the server when opening a conversation but read the info from a 'cache'?

but modding is playing around with the protocol which patchou wouldn't do. so it's up to plugin makers but still i don't think that it is possible

yes it's possible to interrupt the packet flow so that the 'initiate convo' signal is not sent until the user send his first message.
you'd better recommend this feature to the messengerdiscovery guys as it won't be hard for them to implement it.

ya tis hv been a problem for me.. i keep gettin conv notifer popin up like mad everytime i sign in

I would be careful about blocking the initial notification. Knowing a bit about the protocol, if you have the window open for two minutes, the switchboard won't let you chat when you send the first message. It is still possible to implement this feature: you've just got to be careful about it (delay the XFR to the NS until a message is sent). Also, you'll need to avoid Messenger thinking the connection has dropped.