External Harddisk and no Luck with MacOS-X

I have some very strange problems with my external harddisks.
I use a Intel PCs and my PowerMac together. I bought an external USB Harddisk, which works fine on my Laptop and other computers I own, but it doesn't work neither on my PowerMac (G4, 400) nor a brandnew Dual-G5 1800 from a friend.
When I connect the USB harddisk, nothing happens, when I do a refresh in System information the Mac slows down to a crawl.
So I bought another external harddisk, this time with USB and Firewire connectors. Guess what, it works fine on my Intel PCs (both on Linux and Windows). Plug & Play. I created two partitions: A smaller one with NTFS for my personal data and a big one with FAT32 for stuff and things.
I connected it to my Mac and both partitions showed up and I was able to transfer files. The next morning, after starting the Mac, only the NTFS partition is visible on my mac and also trying to connect with USB was without any luck. (On the PC there is no problem)
I didn't find anything on the web, so can anybody help me??? Has anyone had the same problems and did something to fix it???
As I am waiting for my delivery of 2 Mac minis and I know, that I will need external harddisks for them, I am anxious that they will not work on them.
I have the newest MacOSX installed with all updates. And yes, I need FAT32 and/or NTFS, because I am transfering a lot of files to/from Intel-PCs.

sounds like maybe the usb port is fried on that g4, try connecting some other usb device to it and see what happens, also, connect the external hd and go into system profiler and check if it shows that anything is connected to the usb port.

Nope

Macman said:

sounds like maybe the usb port is fried on that g4, try connecting some other usb device to it and see what happens, also, connect the external hd and go into system profiler and check if it shows that anything is connected to the usb port.

Click to expand...

No, the USB port is just fine. I have on this port a external hub connected, on this hub is: the keyboard, the mouse, a bluetooth dongle, my Canon EOS300D, a multi-cardreader.

I tried every port on the mac. even with or without a hub (I too tried different hubs, one USB 1.1 hub (which is my mainhub for the mac) and two USB 2.0 hubs (which works fine with the other stuff both on Intel and Mac)

I just figured the problem with my firewire harddisk out. Somehow MacOSX overwrite the partitiontype for my datapartition. It changed it from FAT32 to FAT. Where WindowsXP seemed to ignore this, the Mac relied on the specification, where a FAT partition cannot be bigger than 2 GB.
So after changing the partitiontype to FAT32 in Linux (with overwriting the partition table and rescuing it after all... gave me some headaches) he likes the whole bunch again ;-)

(And I found out, that I was lucky, because before my Upgrade to 10.3 the Mac wouldn't recognized a FAT32-partition bigger than 128GB)