Big USB Problem on 20" iMAC - Help Please

Hi,

I really hope someone can help, as this is driving me mad.... My USB devices have become 'not hot pluggable'.. i.e. When I boot the Mac up, everything is recognised, and works fine. If I unplug something, then plug it back in, it is not recognised. (PPC for example).

The Mac struggles to find my HP 990 printer too, saying to check connections. I turn the printer off, and back on, and, eventually it is recognised....

I am very new to Macs, but everything was working fine up to a week or so ago, and I haven't messed with any of the System settings or anything.

I have run Disk Utility, to correct Permissions, it did find some problems, but said it had fixed them.

Any ideas where to turn to next? Could it be a hardware problem, which Apple need to fix under warranty.

Any help would be greatly appreciated.

Thanks

This sounds like it may be a problem with the power through the USB ports. Possibly that there is too much of a load for the power available. Have you added new devices recently or are you using an unpowered hub? You may need to go to a self-powered hub.