Driverproblem with GTX 750 ti - Random and nonrandom freezes.

I have a new PC with a GTX 750 ti.
I noticed that the driver crashes everytime when I use specific thinks.
Got a freeze…
…everytime I logged in into a server in Minecraft. (take a few seconds with fpsdrops before)
…sometimes if loaded an image into gimp.
…sometimes if a youtube-videoad before the right video is playing. (in firefox)

Got a crash/logout…
…randomly without any specific action.
…sometimes a few seconds after login into my desktop.

I tryied almost every driver. From nvidia-319 to nvidia-352 with the xorg-xedgers-PPA.
I currently using kubuntu 15.04 with the plasma 5 desktop.

Additional Informations:
‘uname -a’: Linux linus-kubuntu 3.19.0-15-generic #15-Ubuntu SMP Thu Apr 16 23:32:37 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

‘modprobe -R nvidia’: nvidia_352 // (Actual using)

‘tail -f /var/log/syslog’ after crash in minecraft:

‘dmesg’ after random logout:

GraphicscardInformation with Nvidia-Settingstool:

Sorry for my bad english.
I crawled mush sites but didn’t fount an solution.

I already tested the GRUB_CMDLINE… with ‘nomodeset’ and ‘nopat’.

If you want any othe information just say it.
Please help me!

Please follow the steps here:

I failed to generate the log, because after the crash I wasn’t able to interact with the remoteshell.
I had restarted my PC with a KubuntuUSB and grabbed the xorg-Logfile which should conatin the same mesdages. The xServer was started with ‘startx – -logverbose 6’.
The Log-File:

I hope this will help.

Does it happen with chromium, blender, steam etc?
Did you try a window manager without compositing?
Does immediate + vehement TTY switching do anything useful?

Not sure if related, but:

I’ve had similar looking problems + error messages - especially the XID errors look mostly similar - for a long time now and if I manage to change TTY within only a few seconds of the freeze by repeatedly mashing the strg+alt+F[?] keys, it unfreezes almost always after switching forth and back again once. In my case, the freezes can most reliably be reproduced by using a window manager compositing / texture transforming on a chromium window. Don’t know what qualifies for plasma5 though - maybe something that resizes the window or shows small floating previews or something like that.

Also, maybe look here:

I tried it. I had disabled the compositor and loaded Minecraft for testing. The same crash.
It also not worked to switch really often the TTY.
At the moment I think its a hardwareproblem and not a driver fault, because tuxedocomputers also sells computers with this graphics card and also shipping an installed Ubuntu 15.04 on their computers with no problems.
I think the graphics catd isnt connected right or is damaged and the crash everytime happens if the graphics card wants to turn on the fans and is failing.

I’ll ask my store who build my custom PC for a check and a new card.