The return key seems to be disabled on windows8-IE10 on this site when typing in the post window, I also have this issue with another site (revcounter.com) but it seems to work OK on UKMOC or Ducati.ms. I'm typing this on an old XPdesktop BTW, it seems to be a known issue on VB forums.
You need to select a/A button at left (black/blue in colour). Then all is good for that one post. Drives me nuts and was like that since early betas.
That seems to have done it , thanks. Its an extra and unnecessary button push but at least the functionality is back.