hmmm, I think this is a performance problem.
I have the Server running as a VM with serveral other Servers on the Machine.
I have two XEON CPUs on it.
The Hyperthreading slows the VMs even if I give them two Processors.
I stoped the Hypertreading yesterday and gave the ISP Server one "complete" CPU.
Now the ISP Server is faster and the Problem doesn't happen anymore.
But it looks like if the Interface is quite resource intensive.
The Site doesn't stop to load sometimes, I can work and it reacts but the Site is not fully loaded.
I have the suspicion, that the tree (left window) is the source of this porblems.