Filters using custom headers not working?

Hi,

I've been using TB for U3 without any problems but now I installed TB portable on a disk and I've encountered a problem with the filters:

When I specify custom headers to filter my mail on, and I use them, the filters are not executed. While, when using standard headings, they are.

Is there a known problem with the filters in TB portable? Is somebody else having this problem? I've posted my question to other forums and there people responded they do not have the problem...