It took me a day to understand what you meant, lol, i was looking at it too literal.... cat 10.10? ohhh... Catalyst driver 10.10... clocks, overclocked from stock.... Sorry, i really had no idea what you meant initially. Cat 10.10 locked your clocks at stock.... i really thought you meant your actual system clock, as in, time, lol...
Anyway. So you've done all the usual, including a format and get the same problem. After the format, did you use 10.10 again or use 10.9 instead? Is overdrive greyed out or can you activate it but it just won't keep the settings?
For the time being, you could use a 3rd party tool, like the
MSI Afterburner, allows you to clock further than the overdrive tool, as well as overvolt (should you need it). It's basically rivatuner with a new GUI, easier to use, etc. I've lost overdrive support on my GPU's before, yet for some reason, they mysteriously re-appear at some point, very irritating, so just use another tool.