Pytask crashed with "TypeError: can't convert return value to desired type"

I'm using Ubuntu 10.10 Maverick
kernel version: 2.6.35-23-generic
architecture: i686

When I select "Name" > "contains" > (input box) "<a word in my task name>", it shows the right task with the word I typed and even when I select "Add", a new line of options appear to fill in.
But when I select "Priority" > "=" > (input box) "<priority number>", it doesn't show anything at all and Pytask crashes after I click on other applications. Also if I don't put any <priority number> in the (input box) it seems to work fine. Following is the error message when pytask crashes;

DEBUG:root:debug mode enabled...
INFO:root:Connecting to discovered local port.
TypeError: can't convert return value to desired type
/usr/bin/pytask:264: Warning: /build/buildd/glib2.0-2.26.0/gobject/gtype.c:4181: type id `0' is invalid
  gtk.main()
/usr/bin/pytask:264: Warning: can't peek value table for type `<invalid>' which is not currently referenced
  gtk.main()
Segmentation fault

The attachment contains a screenshot of the options, I'm talking about.