Logic 5, G4 PowerBook : Mac Av: System Overload ..(-10011), Logic 5, G4 PowerBook : Mac Av: System Overload ..(-10011) Options

Hi,

I have recently acquired a lovely 667Mhz G4 Powerbook, with 512 Mb of RAM and 30GB Hard disk.  I am trying to use Logic Platinum 5.1.3 but as soon as I kick off more than a couple of Audio Instruments (Evoc, EXS24) I keep running into the message :

'Mac AV:
System Overload
The Audio engine was not able to process all required data in time
(-10011)'

Can anyone give me any ideas as to how I might get around this?  It's driving me nuts!

Thanks in advance

Phil