How to fix word 07 list problem?

I have got a problem which I cannot explain properly. I have been working with word 2007 both on my PC and Laptop. But I get problems when I work on lists.
On the PC, if I create a list, say a) list and type in text, then press Enter then the b) appears as it should. If I do not type text and press enter then the b) disappears and my text returns to normal, which is how this should work. If I press enter again then the cursor moves down to a new line.
On the Laptop If I create the same list a) and type in text, then press Enter then the b) appears as it should. If I do not type text and press enter nothing happens. The cursor stays where it is and doesn't move. If I press enter again still nothing happens. This only seems to be doing this with the lists. The other heading styles are working perfectly.
I have checked the basic settings on both machines and they are set up the same. I also have Word 2003 running on the laptop and the lists are working as they should in that version of Word.
Had anyone ever experienced this? If anybody solved this problem, Please help me.
Thank you all.
