>16GB free on my C drive
Is that your ONLY drive?
Even if you have the required/advised separate drive for video files, only 16G free on your C drive COULD be your problem... since depending on where your temporary files are stored, you MAY simply be running out of working space when PPro tries to create working files
Drive C space http://forums.adobe.com/thread/1007934?tstart=0
If you do not have a separate data drive... never a partition http://forums.adobe.com/thread/650708 for more on partitions... you need to buy/install a 2nd 7200 rpm drive for your video files
My 3 hard drives for video editing are configured as...
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1 - 320Gig Boot for Win7 64bit Pro and ALL program installs
.
2 - 320Gig data for Win7 paging swap file and video project files
When I create a project on #2 drive, the various work files follow,
so my boot drive is not used for the media cache folders and files
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3 - 1Terabyte data for all video files... input source & output export files