I live in the southeast US. I first started hearing "flustrated" by local speakers a few years ago. It was apparent that the speakers were not using this for comic effect; the speakers were quite angry at the time.

I don't think that it's a combination of flustered and frustrated...just a variant pronounciation of "frustrated". If you look at the examples used by the other contributors on this site, I think that they illustrate the use of this term as "frustrated".

I couldn’t care less (but one must keep up appearances, right?)

Flustration is wrongly spelled Frustration.

This mistake possible came from the attempt to join words frustrated and flustered which is senseless.

See other translations.
(Note: they are wrong.)

1) To become frustrated and flustered at the same time cauz you cant get what you want 2) to be like Neil

To be frustrated and flustered at the same time.

Flustered & Frustrated combined into the one word to describe a combined feeling of both emotions.

A made up word apparently by southerners, which combines "frustrated" with "flustered"