Well yes, I have about a 25-33% failure rate these days with sending/receiving offline IMs these days. It really sucks. I now both IM and notecard anyone I'm trying to get ahold of, but god knows how many potential customer IMs I'm missing because offlines aren't working well nowadays. Drives one mad.
I'd much rather answer simple questions via email than delay until I log in to do it. I'll start replying again, and add a note to let me know if they got it.