I've been having a problem with Excel.  When I convert from portrait to
landscape, the program refuses to print, freezes up, gives me print spooler
errors and memory write errors and also causes some of the other programs
unrelated to Excel to refuse to open or work properly.  I'm using Office 2003
Student/Teacher.  If I recover my system, shut it down and restart, the
problem goes away and i can open non-offending spreadsheets just fine in
Excel.  I've tried opening the offending spreadsheets with a 2007 version of
QuatroPro, but QP gives me a "runtime error".  The sheets can be opened and
read on the monitor in Excel, but I can't print them or do anything with
them.  

I know this sounds like a virus problem, but both Norton and AVG tell me I'm
virus free.

Any suggestions would be sincerely appreciated.