using vba in autocad2008, calling to excel 10

I have a class that wraps various excel functions
I use it to display results of some process in spreadsheet

the excel objects are being correctly created and data is entered in
spreadsheet as it should be.

sometimes when excel app shows (.visible = true) the client area is
"transparent", that is,
whatever windows are behind excel are seen where the spreadsheet should be

if it manually View|Full screen the client area paints correctly and I can
then close full screen to get back to normal

is there a way to programatically get excel to "refresh" itself?

curious, is there a reason why this would happen sometimes and not other
times?

thanks
mark