It could be known problems with the latest version of OSX 10.4.9 and/or that your system is a little underpowered. Here is a recent report:
AU Plugin Vendors: Hold Off On OSX 10.4.9 Upgrade
According to Gearwire:
"...something appears to be amiss with Apple's most recent OSX software upgrade, 10.4.9. Plugin maker Ohm Force sent the following to Gearwire...)
Important Note Caution: the installation of 10.4.9 can empcher the operation of our plug-ins AudioUnits. 10.4.9 installs a new version of auval, with which our plug-ins WITH is incompatible. We did not think that this version would be publi?e before the exit of 10.5 We wish to put a new version? day which will pass the validation within 3 weeks. Meanwhile, we advise you not to install 10.4.9. While it could be made clearer, it seems that Ohm Force is advising users to not apply the 10.4.9 upgrade specifically due to changes in the AU subsystem.