Weird and huge CPU consumption with no patch open!

Hello,

I am running MaxMSP 4.5.7 under MacOS X 10.3.8 on a G4/867 MHz
TiBook with 768 MB of RAM and a 100 GB/7200 rpm HDD.

I wanted to show someone the difference between the CPU
consumption showed in the DSP Status window and the
consumption showed by the "top" app in the terminal (which is
suppoed to include activity of the scheduler). I was quite
surprised to discover that with not a a single patch open and
audio off, MaxMSP was eating much CPU, with values evolving
randomly from almost 0 % to more than 70 %.

I have tried the following without any result :
- discarting externals;
- removing patches in the "extras" folder;
- quitting and relaunching;
- starting and stopping audio.

The problem remains also after reboot of the computer.

Any clue?

Roald Baudoux