Curve fitting diaLOG IS too SLOW TO OPEN

Hi

IgorPro 6.3.7.2 on Windows 8, Intelcore i7 3770@ 3.4Ghz
Is there a solution to this? I use two user defined curve fitting functions. I fit about 120000 points of data in segments of 100 points. when i click Analysis ----> Curve fitting it takes around 2-3 minutes to open the dialog box resulting in a loss of about 200-300 minutes ! ! !