Question: Blank worksheets in Maple 12/linux?

I've just installed Maple 12 on my machine running Suse 10.0, under which Maple 10 ran with no problems.  But I have two problems here: even on a newly opened worksheet, in a newly opened Maple, a simple command, such as

f:=x/(x^7+1);

takes several seconds to "evaluate", while the screen goes completely blank.  The problem is even worse if the evaluation is a difficult problem.

What seems to make it worse is if I've read in some Maple files before with

read("myfile.mpl");

and then a simple variable assignation (such as above) takes even longer - up to 10 or 15 seconds.

So the two problems are: 1) time taken to evaluate even a variable assignation, 2) screen going blank while it does so.

Does anybody know what's going on here?

Thanks,

Alasdair