I'm trying to do a four image merge to 'HDR Pro in Photoshop' from Lr4. When I do this I get the error message, 'There is not enough space on the default volume to complete this operation'. I tried cutting back to three images and got the same error message, though this process has worked with three images before. I checked the preferences>performance settings and I have 7175MB of RAM available and over 400GB of scratch disk space. I searched the web with the error message in quotes and found no posts or comments closely related to the problem.
Any ideas what this is and how it is resolved?