At least happens to me and it was quite annoying until I understood that the filter was (de-)activated without the checkbox changing it's status.
To reproduce:
1. Open the trade office
2. Uncheck all trade filters (net necessary to reproduce but it's easier to see the effect by doing that)
3. Move the cursor of one of the filter checkboxes (eg. buffs), the checkbox should get focus on event
4. Move the cursor to the right so the check box 'loses focus'
5. Click left mouse button - Suddenly the buffs appear, but the buff filter checkbox remains unchecked.
This works the other way round - ie. if the checkbox is checked, clicking right of it will remove the filter but leaves the box checked.
Probably the fix is to adjust the area of effect.
Using Windows 7 Pro 64bit, Firefox 20.0.1 and Shockwave flash 11.7.700.202
Best regards,
SirLoxley