MAC will not recognize My Book Essential Editions

My Mac PowerPC G5 OS X ver 10.5.6 no longer recognizes my 500gb My Book Essential Edition WD5000H1U. I have a MyBook Studio also on this macine and it recognizes it.

I took the drive to the Geeks at Best Buy and their PC recognizes the drive and can see all of the files.

Took the drive back home reconnected the drive to the Mac and it worked correctly. I could get the files everything seemed fine.

I had to reboot the Mac and again the drive is not recognized. I’ve tried every combination of connection USB / power/ rebooting cold or hot. I tried Disc Utilities but the drive is not visible.

I read a number of fixes on other threads and tried what I could but to no avail.

Ideas please.

Seems like a faulty drive, call tech support to replace it.