[Hendl]

HELP! I am new - have word 2007.
Often, after I have been typing for a while, the screen becomes "locked".
Whatever I type doesn't appear on the screen at all.
Also the cursor changes its appearance from a
thin, vertical cursor, to a shorter (stubbier) one.
Have I accidently hit a key which does this?
I have tried experimenting with the INS and Pause keys, but they don't seem
to help.
Please - I need help right away!
THanks