In case anyone has this problem too, I fixed it the following way.
I installed a previous robot controller release, which gave me more free temp memory straight away. I don't know why but that helped already a bit. Apart from that I did a backup, deleted all my programs and loaded the backed up files again. I didn't load the DCS files. That saved me a lot of TEMP memory. I had a pretty extensive DCS setup which probable used heaps of memory. Unfortunately I don't have that DCS setup any more now, but that was the only way of getting it working.