enabling multisite results in infinite redirect

[mc0e]

I've got a wordpress site working by disabling the multisite feature.

Previously it showed an infinite redirect loop with http://wpadmin.[mydomain]/wp-signup.php?new=wpadmin.[mydomain] redirecting to itself.

re-enabling multisite in puppet breaks the site again, and disabling it again fixes it (once puppet runs of course.)

Any suggestions?

I'm new to wordpress - probably doing something that seems silly to someone in the know.