how to fix mac lion error -600?

First , take your system serial number out of your profile, you don't need to broadcast that.

That error code means that there is no eligible process with a specified process serial number. Do you have a trial copy of some program that has expired?

The only online reference I can find to that error code refers to OS 9 and below. Is this what you're refering to? The questioner explicitly mentions Mac Lion, not < X.

Use the "Search communities" box above for 'error 600' (without the quotes). It doesn't come up often, however, the consensus is that it is a process issue.