MS-6547, USB2 PCI card intermittent detection

To anyone who can help,

This is my first time at this so I apologise if I fail to use the right etiquette. Feel free to correct me in anyway.

I have installed a 5 port USB2 card in a spare PCI slot in my MS-6547 motherboard running AMIBIOS 1.6. Computer runs XP-SP2 and detects the card, I get all the right signal...enhanced USB controller etc... However sometime when I plug in a USB2 Memory stick device I get one of the following:
1. Normally it works fine
2. Quite often the light on the stick comes on and just stays on, with the computer showing no indication that anything is plugged in.
3. Very rarely it tells me that this device would work better in a USB2 port and shows me that there are four available ports even though the device is plugged into one of them.

It is not just a memory stick, it is a bluetooth dongle and my adsl modem. Which mean I can only sporadically comnnect to the net. I have to keep switching computer on and off till they work. I can't upgrade BIOS as I have no floppy drive

Thanks for any help
Lee