keryx hangs downloading when the file is already exists

Why sometimes Keryx cannot download repositories' lists and returns "Using proxy: {} Download error: time data 'Fri, 30 Nov 2012 07:41:00 GMT' does not match format '%a, %d %b %Y %H:%M:%S %Z'" for each item in list? Lubuntu 12.04, direct connection. Internet connection is OK other apps works well. Keryx run via console without sudo. Version Keryx 1.0-public21
UPD: I noticed that keryx hangs with downloading if the package or repository list is already exist. Deleting existing item makes keryx to work well but gives problems with packages (sometimes too many to delete). It seems to be a bug, please fix it.