It may have something to do with ISPConfig being not properly installed, but that has nothing to do with available diskspace. The output of df -h:
Filesystem Size Used Avail Use% Mounted on
simfs 100G 5.0G 96G 5% /
tmpfs 1012M 0 1012M 0% /lib/init/rw
tmpfs 1012M 4.0K 1012M 1% /dev/shm
More diskspace than money
Two extra bits of information:
- I have the same problem on two different machines, running two different editions of Windows Vista Ultimate (one 32 bit and one 64 bit) but the same version of Firefox.
- Last weekend I updated ISPConfig from version 2.2.14 to 2.2.21. The problem was already there before the update and is still there after the update.