Ubuntu Installation :: Errors: Error 404 In IIRC 3 Different Places Then Came Another Error

I installed Double Commander only to find that it was broken and couldn't launch. So searched and found it was a known problem and fixed already in unstable version. There is a build on Launchpad.So:

Code:
sudo add-apt-repository ppa:alexx2000/doublecmd It finished fine. When I reloaded my Synaptic window, it did some work and I saw the first errors: Error 404 in IIRC 3 different places. Then came another error, I didn't understand it and clicked a button. Synaptic closed. I think I know what was the 2nd error because no every time I start Synaptic, it shows a message and after I click the only available button (Close), it quits. The message is:

Quote:

E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/apt/lists/
pl.archive.ubuntu.com_ubuntu_dists_natty_main_bina ry-i386_Packages
E: The packege lists or status file could not be parsed or opened.
E: _cache->open() failed, please report.