Happens to me all the time... I copy some text from Word (either right click or Ctrl-C) and past it onto a text layer in AE and it either does nothing or pastes the last lot of text I copied previously. Seems to work fine if I do it a second or third time, or alternate the left click, Ctrl-C action.
Bit of a pain as I'm working on a project for 116 videos that each have about a dozen or so lines of text in them. So it may only add a few seconds on to what I'm doing, but that adds up to over an hour of extra work. An hour I could have spent by the pool sipping cocktails and making plans for world domination.