A few months back Matt Munslow posted an article 'Timer Job Shocker'. This post mentioned how IIS Manager failed to open and Event ID's 7076, 6398 and 6482 were appearing in the event logs repeatedly with a message: "Attempted to read or write to protected memory".
Microsoft has now found the root cause of this problem to be the IIS ADSI provider. Essentially, if you have a process with more than one thread and two threads access IIS 6.0 at the same time, then this issue occurs.
This problem is likely to occur for the SharePoint Timer service (OWSTimer.exe) in Microsoft Office SharePoint Server 2007. When this occurs, you may find that:
In SharePoint Server 2007, tasks that are scheduled do not run.
When you try to manage IIS 6.0 by using Server Manager, you receive a blank page, or you receive the following error message: "the path specified cannot be used at this time".
The Event ID's 7076, 6398 and 6482 and memory error messages described above will also be recorded in the Application Event Logs.
Microsoft now has a KB article describing this problem http://support.microsoft.com/?id=946517 along with details of the fix and how to obtain it.
This fix is an IIS fix so you should be able to install the fix regardless of what SharePoint Service Pack level you are running.
Update - There is a known issue with the IIS fix and the SMTP service which results in any configuration change made to SMTP generating the error SMTP Configuration - Unspecified Error. This is fully documented and a fix is available from http://support.microsoft.com/kb/950426