G3 won't recognise USB peripherals.

[pgrachev]

My 900MHz G3 is clearly playing up: whenever I plug in a peripheral device (external HDD or a mobile phone) through either of the USB ports, Finder will not display a disk image, so I can't establish a connection between the hardware and the Mac. I have tried rebooting - no avail. Disk Utility shows nothing is connected, like Finder, although System Profiler says the device is recognised as it should be. I'm puzzled. This was never a problem before. Please help!

Thanks.
Pasha

 

[pgrachev]

The mentioned peripherals are recognised by PC, so the problem is obviously not with them or the USB cables.