** Using WeBWorK **

You can turn the mechanism that automatically deletes temporary files off using the instructions at

http://webwork.maa.org/wiki/Troubleshooting_Hardcopy

-- this will allow you to inspect to whether the equation .png is not being created.

The most likely command that is failing is mv -- so either it can't find the equation .png file and perhaps it has not been created or else it isn't able to copy the file into its htdocs/tmp/equation destination (check that for permissions as well).

With the temp files not being deleted you can try to mv things around using the command line tools which might give you more information -- just remember that your personal permissions might be different from the webservers -- you can fix this by issuing:

sudo su apache

now you are acting as the webserver and should have the same permissions -- that might give you more clues. (type exit to get out)

If the .png file is not being created -- then I'm less sure what to check next.
Try running bin/check_modules.pl -- that might pick up a missing module or a bad path to an application.

hope this helps.
Take care,

Mike