I definitely plan on getting a PS meter. I RMAd the new card because I wasn't sure if it was a dud or not, especially since the fan flipped the hell out after a while.
Just now, on my 4850, I was watching two synced youtube videos and my video driver died for a second but recovered. The card isn't overheating at all though.
Aurora R3 - Intel Core i5 2400 | 8GB DDR3 PC 10700 Kingston | PLDS DVD+-RW DH-24ABS | ATI Radeon 6870 1GB | Monitor: ASUS 24 inch LCD | 1TB SATA2 7200rpm | Windows 7 Professional SP1 64bit | Realtek HD Audio Intergrated
I had the exact same problem with my Aurora ALX a few month ago, replaced the PSU with a 1000w PSU I had in an old XPS 730 and the problem was resolved. Mega stable since.