Excel calculation (by ActiveX) suddenly runs slow

Hi,

I have a Matlab code running ActiveX Server to do Excel computation. The code create a new spreadsheet, retrieve data from SQL database and feed into the spreadsheet. There are lots of formula in the spreadsheet. To save time of formula recalculation, I set the calculation mode to 'manual', and the code instructs the sheet to do re-calculation when it is needed.

In last two months one run of the code took about 20 minutes, which is normal. However, a few days ago, the computing process suddenly became very slow, totally takes > 100 minutes. The later the stage, the slower the computation.

It is wired that if I run same code on other machines with even lower hardware configuration, the running time is still around 20 minutes. So I think optimizing spreadsheet to speed up Excel calculation is not the way to go. It must be something wrong with my computer.

Anyone can have some suggestions solving this issue? Thank you very much.