FFXIV & R9 290X Troubles

[Morgwyn]

Excuse my English - it's not my native language

Problem:
I'm not able to play FFXIV with my "new" Sapphire Tri-X R9 290X.
There are 2 things that happen:

1. The Game does not start.
   Press the "Play" button, the launcher disappears and nothing else happens.
   After restart my System (win 8.1) sometimes, once in a while, i have luck and it works. But now there is Point 2.
2. Where are the frames going?
   The game will not run smooth. Frames are jumping between 130fps and 1fps, horrible. Changing graphic options and/or set a fps limit make no difference.

I tried different graphics-driver (stable, beta, older ones, etc.) and operating system win7 (64bit). Nothing helped. I set up my System (win7 64bit & win8.1 64bit) several times, because I thought something could have went wrong.
Other games work perfect - no problems.

No component is overclocked. Hardware runs standard clock.

Graphics-Board: Sapphire Tri-X R9 290X
CPU: AMD-FX8350, 8x4.00GHz
Mainboard: Gigabyte GA-990FXA-UD3 (BIOS up to date)
RAM: GeIL EVO Corsa 2x4GB, DDR3-1866, CL9-10-9-28
Power-Supply: Thermaltake 750W

With my old Graphics-Board (AMD 7970) I had no problems.
Hardly ever FFXIV stopped working with a windows message.

What am I overlooking?

I hope someone can help me to escape from my personal FFXIV gaming hell
Thank you for every Idea & Tip!

Uninstall FFXIV and deactivate my SquEx- Account is neither an idea nor a tip