Latest Calibre and Fedora 12 Issue

[Boricua]

Hi, first post here . I am running Fedora 12 64 bit, fully updated. I searched but found nothing like this issue I am dealing with.
I use calibre to access my Sony PRS-600 Touch, which I feed with legal documents in .pdf format for use in court. Due to a bug in calibre that prevented it from starting under Fedora, I installed the latest experimental version available for Fedora (0.6.42). Problem solved. Now, the issue is that, whenever I select a book or a document in calibre's main window, the hard disk starts spinning without pause for around a minute, bringing the whole computer almost to a halt for that long. Even if I close calibre, my computer remains sluggish and showing delays that force me to reboot. I once started calibre from the console and got this output:

[Francisco@Hogar Desktop]$ calibre
link  hasn't been detected!
link  hasn't been detected!
Exception in thread Thread-9 (most likely raised during interpreter shutdown):
Traceback (most recent call last):Exception in thread Thread-4 (most likely raised during interpreter shutdown):
Traceback (most recent call last):
 Exception in thread Thread-5 (most likely raised during interpreter shutdown):
Traceback (most recent call last):
  File "/usr/lib64/python2.6/threading.py", line 525, in __bootstrap_inner
  File "/usr/lib64/calibre/calibre/gui2/device.py", line 172, in run
  File "/usr/lib64/calibre/calibre/gui2/device.py", line 134, in detect_device
  File "/usr/lib64/calibre/calibre/devices/scanner.py", line 140, in scan
  File "/usr/lib64/calibre/calibre/devices/scanner.py", line 86, in __call__
<type 'exceptions.AttributeError'>: 'NoneType' object has no attribute 'listdir'
Exception in thread Thread-3 (most likely raised during interpreter shutdown):
Traceback (most recent call last):
  File "/usr/lib64/python2.6/threading.py", line 525, in __bootstrap_inner
  File "/usr/lib64/calibre/calibre/utils/ipc/server.py", line 166, in run
  File "/usr/lib64/python2.6/Queue.py", line 177, in get
  File "/usr/lib64/python2.6/threading.py", line 252, in wait
<type 'exceptions.TypeError'>: 'NoneType' object is not callable
  File "/usr/lib64/python2.6/threading.py", line 525, in __bootstrap_inner
  File "/usr/lib64/calibre/calibre/gui2/device.py", line 445, in run
  File "/usr/lib64/python2.6/threading.py", line 115, in acquire
<type 'exceptions.TypeError'>: 'NoneType' object is not callable
  File "/usr/lib64/python2.6/threading.py", line 525, in __bootstrap_inner
  File "/usr/lib64/calibre/calibre/utils/ipc/server.py", line 166, in run
  File "/usr/lib64/python2.6/Queue.py", line 177, in get
  File "/usr/lib64/python2.6/threading.py", line 252, in wait
<type 'exceptions.TypeError'>: 'NoneType' object is not callable
[Francisco@Hogar Desktop]$

The first two lines (link hasn't been detected!) were the only ones showing up when using calibre. The rest appeared after closing the program.
Every other function in calibre seems ok, including the settings window. Other symptoms I got are a slower startup time and in adding new books. If further info is needed, just let me know. Any hint will be appreciated .