Rebuild Permissions: An error occurred. /batch?id=27&op=do

Installed CA, ACL, & uc_node_access on a D6.10 site. After enabling modules I get:

HTTP POST is required.
The content access permissions need to be rebuilt. Please visit this page.

When I click the link I'm prompted to rebuild permissions then:

An error has occurred.
Please continue to the error page
An error occurred. /acd6/batch?id=27&op=do

Then on that page:

HTTP POST is required.
The content access permissions have not been properly rebuilt.
The content access permissions need to be rebuilt.

Also not seeing any access options in nodes or admin.

What could be causing this?

You help is appreciated.