Ug...Floating Illegal Operand...leave me alone!

[randomguy79(at)yahoo.com (Matt)]

Hey everyone,

I'm rather new to the world of IDL...so bear with me.  I've been
attempting to debug a program all afternoon...but the damn "Program
caused an arithmetic error: Floating illegal operand" message won't go
away no matter what I do.  I've narrowed the problem down to an
expression in the following form:
a=a+((b*c)/d) where all the variables are of DOUBLE precision.  They
were originally FLOAT but I changed them all and thought it may have
been the problem, but apparently it wasn't.

A little more detail on the program:  I'm working through about 73
datasets using a for loop.  The expression above is embedded in an
additional for loop so as to perform some manipulations ((b*c)/d) on
arrays and sum all these manipulations into 'a.'  The interesting
thing is, I can run 1, 10, or even 72 datasets and not get the
"floating illegal operand" error.  Only when I run all 73 datasets at
once do I recieve the message when the program is complete.  I'm
getting results as well...I just question whether or not they're right
because of the arithmetic error.

I'm not sure if the Check_math function would help out here or not.  I
tried using it earlier but I couldn't actually figure out how to use
it properly.  Can anyone help me out here at all?  Either helping me
diagnose this or helping me figure out how to use the check_math
function?  I'm really stumped and extremely frustrated.  Thanks.

Matt
randomguy79@yahoo.com