Temp files sometimes not created during build in uVision 5

I run an undergraduate laboratory where we use Keil uVision 5 to compile code for an LPC1768. Frequently, students will see errors that look like this:

"no source": Error: command-line:  #564: cannot open embedded assembler output file "C:\WINDOWS\TEMP\p2b1c-2": No such file or directory

src\p1_main.c: 0 warnings, 1 error

I understand from a previous post on this forum that it is a Windows account thing and not a Keil thing, so I'm working with our IT department to figure it out. However, no one seems to know what these files are, and they do not exist on any machine (even machines that do successfully build the code), as far as we can tell. 

Can anyone shed light on what these files are, and how/when they are created? Our best guess at this time is that Keil is writing to a folder that has write protection when it shouldn't, and only some accounts are affected. If I'm right about that, then I am happy to just change settings in Keil so that it writes to a folder that any user should be able to access. However, I don't know where this setting might be or even if it exists, so any help would be greatly appreciated.