Ever since i upgrade from 4.8.1 a strange thing appens

I use LW from my office
My connection is only free from 9am to 9pm
Every night i must disconnect LW
Every day the progress D/L of big files .avi or .mpg is reseted to lower value than the previous day
While i use 4.9.11 the reset was random
In 4.9.23 allways reset to 2%
After D/L restarts i have allways the message "file corrupt"

Anyone with the same problem??