Please Help!

I am using Excel XP with Windows 2000.

If I have "Caps Lock" on OR if I type in all caps by
holding down the "Shift" key WHILE typing directly into a
cell on any spreadsheet (even a new one) the text is
displayed vertically, like this:

E
X
A
M
P
L
E

It is terrifically hard to enter text like this. When I
press "Enter" the text resumes its normal horizontal
appearance. It just started doing this and I have checked
all the options settings, etc. and can find nothing wrong.

Again, let me stress that this occurs AS I AM TYPING and
before I press enter. In lower case/mixed case, it doesn't
do this, only in all CAPS!

Any clues what is going on? Is it my keyboard, video
driver, a corrupted Excel driver or what?

Thanks in advance for your assistance.