no I dont think any card is any more likely to fail in an oc than any other, just one might oc better than another
The biggest thing you have to worry about is heat so get a utility to measure your gpu temp. I recommend Rivia Tuner, it can oc the card too but I just use it bc it puts a nice graph of my gpu temp fan speed, memory speed and clock speed (all for graphics card) and it can record your temps while you play a game or its idle temp. below is a link to Rivia tuner
http://download.guru3d.com/rivatuner/
now for some tips, play a game for awhile with rivia graphing temps of your card at stock speed see what it tops out at. Bring up ATItool and open the 3d view, with rivia running, and let it go to see what temps your card tops out at.
keep a record of those temps, i just remember them mostly the atitool temp bc it is going to be hotter. ATItool 3d view stresses a video card very well and more than a game will, trust me it may not look all that impressive but its more than a video game stresses. Also take note of the fps in the 3d view.
now the fun part ocing. just bump up the clock speed first 10mhz or 20mhz at first and then test with atitool (use the test for artifacts in ati tool) once you hit a wall that the card cant go past start bumping up the memory speed till you hit another wall and there you go its basically that simple. oh and keep an eye on those temps, I don’t know what your card can handle but you should be able to hit 80c or so with out any problems.
if you want to do it an easy way just use the "find maximum clock rate" button or what ever its called and ati tool will slowly bump up the clock rate and shouldn’t oc it beyond what the card can handle. it has one of these for the memory as well.