Warped screen and Black-Grey Bars

[P R E D A T O R]

I recently overclocked my AMD Radeon 7550/7650M card using MSI Afterburner. Although while in-game, the screen got stuck with blackish grey bars and required a forced reboot. Why did this happen and what can I do to make sure that this doesn't happen again?
I am using a laptop (Sony VAIO) so I cannot change my voltage settings. I can only move the Core and Memory Clock sliders.
Also, how do I find out the right settings for overclocking? I tried finding some benchmarks for this card but I couldn't find any.
Please help.

 

[StubbleyBeard]

To how far did you set the core and memory clock? The 'blackish grey bars' indicate artifacts. Meaning when you get artifacts you do not have a stable overclock. The forced reboot is probably your GPU shutting down to prevent any further damage / harm.

I suggest you go gather information about your card first before starting to overclock, yet learn how to do a -proper- overclock with that card.

 

[P R E D A T O R]

Initially, I increased the core clock from 500 to 600(maxes at 650) and the memory clock from 900 to 100 (maxes out at 1170). At these settings there was no improvement in FPS at all (tested in Dota 2 and F1 2013). Then I tried maxing out all these values (as they were already very close to the right end of the slider), and this caused the bars.
I can't find benchmark logs anywhere. How does one find out the correct balance?