I encountered this with an attempted install of 10.04 LTS from XP SP3.

Some items of note:
- This failed very soon into  the download attempt
- I'm hanging off a connection that blocks all bittorrent traffic
- C:\\ubuntu\\install\\ubuntu-10.04-desktop-amd64.iso is a zero-byte file at the time of the error

It appears that after btdownloader fails, we don't catch the error and fallback to a basic http get, instead we log: "DEBUG  TaskList: ### Finished download".

Here's the tail of the log:
[...]
05-02 11:21 DEBUG  TaskList: ### Finished get_metalink
05-02 11:21 DEBUG  TaskList: New task download
05-02 11:21 DEBUG  TaskList: ### Running download...
05-02 11:21 DEBUG  btdownloader: downloading http://releases.ubuntu.com/10.04/ubuntu-10.04-desktop-amd64.iso.torrent > C:\ubuntu\install\ubuntu-10.04-desktop-amd64.iso
05-02 11:21 ERROR  TaskList: Traceback (most recent call last):
  File "\lib\bittorrent\RawServer.py", line 229, in listen_forever
  File "\lib\wubi\backends\common\btdownloader.py", line 70, in error_callback
DownloadError: Traceback (most recent call last):
  File "\lib\bittorrent\RawServer.py", line 221, in listen_forever
  File "\lib\bittorrent\Rerequester.py", line 96, in fail
  File "\lib\wubi\backends\common\btdownloader.py", line 70, in error_callback
DownloadError: Problem connecting to tracker - <urlopen error (10060, 'Operation timed out')>

Traceback (most recent call last):
  File "\lib\wubi\backends\common\tasklist.py", line 197, in __call__
  File "\lib\wubi\backends\common\btdownloader.py", line 79, in download
  File "\lib\bittorrent\download.py", line 303, in download
  File "\lib\bittorrent\RawServer.py", line 256, in listen_forever
  File "\lib\wubi\backends\common\btdownloader.py", line 70, in error_callback
DownloadError: Traceback (most recent call last):
  File "\lib\bittorrent\RawServer.py", line 229, in listen_forever
  File "\lib\wubi\backends\common\btdownloader.py", line 70, in error_callback
DownloadError: Traceback (most recent call last):
  File "\lib\bittorrent\RawServer.py", line 221, in listen_forever
  File "\lib\bittorrent\Rerequester.py", line 96, in fail
  File "\lib\wubi\backends\common\btdownloader.py", line 70, in error_callback
DownloadError: Problem connecting to tracker - <urlopen error (10060, 'Operation timed out')>


05-02 11:21 ERROR  TaskList: Non fatal error Traceback (most recent call last):
  File "\lib\bittorrent\RawServer.py", line 229, in listen_forever
  File "\lib\wubi\backends\common\btdownloader.py", line 70, in error_callback
DownloadError: Traceback (most recent call last):
  File "\lib\bittorrent\RawServer.py", line 221, in listen_forever
  File "\lib\bittorrent\Rerequester.py", line 96, in fail
  File "\lib\wubi\backends\common\btdownloader.py", line 70, in error_callback
DownloadError: Problem connecting to tracker - <urlopen error (10060, 'Operation timed out')>

 in task download
05-02 11:21 DEBUG  TaskList: ### Finished download
05-02 11:21 ERROR  TaskList: [Errno 13] Permission denied: u'C:\\ubuntu\\install\\ubuntu-10.04-desktop-amd64.iso'
Traceback (most recent call last):
  File "\lib\wubi\backends\common\tasklist.py", line 197, in __call__
  File "\lib\wubi\backends\common\backend.py", line 493, in get_iso
  File "\lib\wubi\backends\common\backend.py", line 348, in download_iso
OSError: [Errno 13] Permission denied: u'C:\\ubuntu\\install\\ubuntu-10.04-desktop-amd64.iso'
05-02 11:21 DEBUG  TaskList: # Cancelling tasklist
05-02 11:21 DEBUG  TaskList: # Finished tasklist
05-02 11:21 ERROR  root: [Errno 13] Permission denied: u'C:\\ubuntu\\install\\ubuntu-10.04-desktop-amd64.iso'
Traceback (most recent call last):
  File "\lib\wubi\application.py", line 56, in run
  File "\lib\wubi\application.py", line 130, in select_task
  File "\lib\wubi\application.py", line 156, in run_installer
  File "\lib\wubi\backends\common\tasklist.py", line 197, in __call__
  File "\lib\wubi\backends\common\backend.py", line 493, in get_iso
  File "\lib\wubi\backends\common\backend.py", line 348, in download_iso
OSError: [Errno 13] Permission denied: u'C:\\ubuntu\\install\\ubuntu-10.04-desktop-amd64.iso'