hmm lets see here.
i have seen those o/c's before on a 7600gt. what kind of cooling solution are your running on the card?
I've never heard of freestone stability test before, personally, i use 3dmark 05 or 06, looping a gfx test like proxycon or something. if it runs for a coupla hours without any visible artifacts, crashing, or significant overheating, you should be good.
also, i've found that the built in nvidia oc tool isn't that hot. try the latest atitool beta, it should work with your card. personally, i don't use it because it artifacts bad (yellow dots up the kazoo) with my 7900gt, but it might work with yours.
also, one more thing to keep in mind: initially, it'll seem like your card can hold the o/c. i used to have an ati x300 at one time, a real pos card. to get a bit more life out of it (before the 7900gt), i clocked it up 75% mem, 25% clock. it hold perfect, no artifacts, no problems in 3dmark and the whole bit.
for the first few months
after the oc set in a bit, i got massive screen corruption, massive amounts of artifacting, and general bad-ness. eventually the card up and died (i don't blame it).
moral of the story: o/c down a bit from the max oc your card can hold. it'll last a LOT longer.
and keep a close eye on temps. for ref, my non-oc'd 7900gt is idling right now at 40C, load at 55-60C in atitool.