可以这样说：
I'm sorry I didn't get your message you sent before,maybe there were some problems with my computer or something went wrong between our two operation systems.
这样他一定清楚!我就经常和老外在msn聊.如果你觉得这种情况不是经常发生,就加一句：
but it's ok.it doesn't happen often.
如果经常这样,就上网下个英文版的.