if both drives are showing up, but not accessible, it's very strange. Looks like both modules are loaded properly and 2 LUNS are exported to USB host, but no partitions are exported as LUNS targets.

Could you, after connecting device to desktop (and ensuring that two drives show up), try to run this piece of code in N900 (as root), line by line? In case of errors after any line, write it here.

After both modprobe -r, drives will disappear from desktop - it is normal. One will re-appear after modprobing again, but still inaccessible. Final command (echo'ing) should make MyDocs accessible. Remember, /dev/mmcblk0 is *not* a typo, in this case, it should be like that, *not* mmcblk0p1.

Use auto-completion for path in final command, to avoid typos - I've written it by hand, so could do some typos, too (although checked it and wasn't able to spot any).

If all commands return no errors, but mydocs is still not accessible, it is really broken hardware'ishly, in some strange way (unless state of system on that device is total fubar)..

/Estel

Thank you so much for this how-to!!!
Usb port of my 26 months old N900 was still fine (I filed down usb plug's hooks since day one and always plugged and unplugged very gently), but as the warranty expired I wanted to try this strengthening technique to stop worrying about this issue. It was quite easy, thanks to these step-by-step guides! That's really a great community.

I'm from Italy, and if someone living near La Spezia needs help with this soldering, I will be glad to help.

My N900 also had the vibration issue (motor not rotating), which I was able to fix too, but I will write about that on the specific thread

Thanks again!

Update: Success (1/2)
There were 2 Problems, a shortened line and a faulty usb extension cable. After resoldering, everything is working correctly and it can be used as a mp3-player. Thanks for attention and help!
Waiting for a new usb port so i can try my luck on my main phone, nearly killed it at last attempt :/