LaserSoft Imaging

Hi,
I am using an Epson 4990 scanner and trying to use SilverFast V6.4.4r3b. The software is installed without a single error. It starts up without error messages. But when selecting the prescan option the scanner will start warming up the lamp and after a few seconds will start the prescan. Sometimes a part of the picture will com on the screen, is seems like the scanner is scanning the whole glass, but when the scan head is back at the start position, no (further) picture comes on screen. silverfast has to be stopt using the task manager. the led on the scanner keeps on blinking. You have to power down the scanner to be able to use it again. Epson Scan is working normal.
I had a Canon Lite 30 scanner on the computer and I have removed that software, including Epson Scan and the Twain driver and reinstalled the EpsonSCan/twain driver and SilverFast, but nothing changed!
Can you help me?

Try removing the SilverFast Prefs.

I use the same software with the same scanner on a Windows XPSP2 computer without this problem, so it does work.