macbook air usb problem

Hi, last day my macbook air usb port don't work well...
I don't know how but if I plug a mouse, pendrive, usb hd the light on the devices is on... I think it's must be ok... BUT I can't use... no mouse no pendrive no superdrive nothing on my desk I don't see nothing.
So I called the apple center near my city and he said that I can try the PRAM
reset... well... but the situation not change... how appened? my air
is never fall down...

thanks for answers.

very thanks jimboutilier,

but after some time, I called Apple and I talk
with a assistance operator... and I realized that my mbair DON'T see any
devices... because in the system profiler, usb section there isn't
anything only the isight camera, bluetooth, ir and so on, BUT my plugged
device... no... for the mac was unplugged!!! the strange thing was that
I run the applecare test "techtool" and the usb passed test!!!
one more time... I realized that was an hw problem... so in late afternoon
I bringed my air and I went in apple assistance center now...
I wait for an email or a call... a last thing my air had only six months..

thanks...

biker