VBA looping: Excel not responding (2007)

Hello,

I ran this VBA earlier and it worked fine (Excel 2003). With upgrade to Excel 2007, I receive the looping problem where Excel is not responding anymore.

For nData = nPeriod To nQuote 
... (Line processing) ...
Next nData

nQuote = approx. 90K (row count)
(Line processing) = from source Excel file (A) create destination file (B) with treatment of lines in A copied to B.

During this looping, my Windows Task Manager shows that Excel is not responding after a while. Then I interrupt VBA with Esc and can relaunch with F5. However, once the last line is treated, it keeps repeating that last line.

I'm not sure how to solve this. Should I treat the 90K lines in smaller batches (units)? How can I do that? Is there another way? Is the rootcause the high number of rows to be treated?