Ctrl-enter is used to enter a line-break in a cell in Calc.  BUT
- it only works when data is being entered for the first time into a cell - if 
I return tot he cell, ctrl-enter works in the same way as enter (accept 
changes, move down to the next cell);
- it does not work all the time if data is pasted into the cell (when typing 
into the formula bar and hiting ctrl-v);
- even when entering data via the keyboard, this feature appears to work on an 
unpredictable basis.

Also, the formula bar does not display line breaks but rather a long continuous 
line of text that goes off the screen (compare with MS Excel)

Contrast with Excel - ctrl-enter seems to always put in a line-break.

Using OOo 2.4, but have seen this on 2.3 and 3.0beta, all on WinXP.