[support] login doesn't work

I can login but if I click anything afterwards it shows me as not logged in (i.e. I don't have permissions and the login form is back on page). It used to work before, not sure what changed (php was updated on my machine) Any ideas how to troubleshoot? I don't see any error message in apache logs, is there some place where I can see drupal errors? Looked at db but no obvious tables with errors/logs. TIA, erik