USB flash memory drive and iMac G5

One of my friends has a digital camera, when connected to her office iMac G5 ...it works fine.
Back home, she plugged-it to her iMacG5...it did not work, not even mount, the System did not see it!!
After spending some times at the phone with her...-> still did not work.
She brought the drive to my place, we plugged it to my PMG5 Dual 2.5GHz ... it worked fine!
Back home, she tried again on her iMacG5...nothing, does not work.
This morning while browsing through the Apple forum I have found the following message:
"Older Lexar flash drive works ONLY in middle USB port not the others"
She tried it...and indeed it worked with the middle USB port of her iMacG5!!