Calibre 6.40 upgrade problem on Ubuntu 9.04

[splashd]

I ran the update script for the calibre binary download. It has always worked painlessly in the past. The download and update worked fine, but when I try and start calibre I get:

$ calibre
link hasn't been detected!
link hasn't been detected!
Traceback (most recent call last):
File "/tmp/init.py", line 48, in <module>
File "/home/kovid/build/calibre/src/calibre/gui2/main.py", line 137, in main
File "/home/kovid/build/calibre/src/calibre/gui2/main.py", line 55, in run_gui
File "/home/kovid/build/calibre/src/calibre/gui2/ui.py", line 580, in __init__
File "/home/kovid/build/calibre/src/calibre/gui2/dialogs/scheduler.py", line 207, in __init__
File "/home/kovid/build/calibre/src/calibre/web/feeds/recipes/model.py", line 129, in __init__
File "/home/kovid/build/calibre/src/calibre/web/feeds/recipes/collection.py", line 128, in __init__
File "lxml.etree.pyx", line 2538, in lxml.etree.fromstring (src/lxml/lxml.etree.c:48266)
File "parser.pxi", line 1536, in lxml.etree._parseMemoryDocument (src/lxml/lxml.etree.c:71653)
File "parser.pxi", line 1415, in lxml.etree._parseDoc (src/lxml/lxml.etree.c:70514)
File "parser.pxi", line 938, in lxml.etree._BaseParser._parseDoc (src/lxml/lxml.etree.c:67438)
File "parser.pxi", line 539, in lxml.etree._ParserContext._handleParseResultDoc (src/lxml/lxml.etree.c:63820)
File "parser.pxi", line 625, in lxml.etree._handleParseResult (src/lxml/lxml.etree.c:64741)
File "parser.pxi", line 576, in lxml.etree._raiseParseError (src/lxml/lxml.etree.c:64256)
lxml.etree.XMLSyntaxError: None
$

[kovidgoyal]

Delete ~/.config/calibre/scheduler.xml

[splashd]

That did it--thanks.
I wish I knew enough to have figured it out for myself.