LR 4.2 export as DNG is slowing down as image count progresses, eventually coming to a halt. Running Windows 7 Pro, i5 core 3.3 ghz, 16 Gigs Memory, 6 terabytes of HD. When converting or exporting Canon RAW images as DNG images, the system will not do more than 500-600 images in a batch and time to convert each individual image grows longer and longer. Coincidently, I've tested the latest external DNG converter (7.2?) and it fails to convert the same files after about 500 or so images do to insufficient memory errors. Diagnostics on PC indicate everything running perfectly. Reverting to earlier version, LR 3.6, everything works perfectly. Using Raw Converter 5.4, everything works perfectly. Problem obviously related to latest releases of LR 4.x and DNG Converter.