That bug has been opened on https://launchpad.net/distros/ubuntu/+source/evolution/+bug/35694

"If I create a custom category to apply to a task and then try to filter my view by category I only get to see the custom category in the drop down list while I am in calendar view. If I switch to tasks the drop down list only shows the default evolution categories. None of my custom categorie are visible.

Whoops, forgot some vital info:

Running dapper, evo version: 2.6.0-0ubuntu3
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> Thanks for your bug. Your description is not clear. How do you create a category? What drop down list are you speaking about?
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I generally create a new category when I need to, usually when I am creating the task I want to categorize. I do the following:

Start evolution
Switch to the tasks view
Click new
Click on the categories button
Click on new
Give the new category a name
Apply it to the task I am creating

All of this works perfectly. the problem arises when I am back in the main view of tasks and I want to filter my view:

I click on the ComboBox "Summary Contains" and select "Category is" from the drop-down list.
Then I click on the ComboBox "Any Category" and look for my newly created category in the drop-down list. It is not there.

If I switch to the Calendar view and repeat this filtering procedure my newly created categories are visible in the drop-down list.

Basically, the problem is that evo has a different idea of what categories are available for filtering purposes dependant on whether I am in Calendar view or Tasks view.

I have discovered this morning that restarting evo gets everything back in sync."