USB hard drive not detected

I have just installed Simply Mepis 6.0 to a friends Acer Aspire 13350 laptop. Everything seems OK but when I plug in his external USB hard drive its not detected. I know it works with linux cos I tried a few live cd's like knoppix and PClos and it gets detected by them.
I tried booting the machine up with the drive plugged in and i get series of errors before mepis eventually continues to boot. If I Plug it in once booted to the desktop, nothing happens.