I have encountered similar problem in stack test suit.
everything is working fine except Maxima Plots. After requesting plot
test several times (switching from alternate to standard and back) it
eventually works. I am not sure what this problem could be related to.
I have tested it on
Ubuntu 9.10 ( Karmic Koala), Maxima versions 5.17.1 and 5.18.1.
Maxima timed out
Problem connecting to the CAS. Please check your settings.
There should be two different plots. If two identical plots are seen then this is an error in naming the plot files. If no errors are returned, but a plot is not displayed then one of the following may help. (i) check read permissions on the tmp directory. (ii) change the options used by GNUPlot to create the plot. Some examples are given in maxima\maximaConfig.php around lines 50. Currently there is no web interface to these options.
If the no errors are returned, but you cannot see a plot above try the following steps:
P.S. Of course I have correct perms on tmp directory.