When using Omega Tools to create a subtheme, on the "Step 1: Theme information " page, I got the same error 18 times:
Warning: file_put_contents(public:///.htaccess) [function.file-put-contents]: failed to open stream: "DrupalPublicStreamWrapper::stream_open" call failed in file_create_htaccess() (line 505 of /Users/kendalltotten/Sites/omega_sandbox (trunk)/drupal-7.x-dev/includes/file.inc).
This is a clean D7 installation. The only module installed outside of core is Omega Tools, the only theme is Omega. I chose the following options on the install subtheme page:
-Base Theme Omega
I was still able to create the subtheme even with the error messages, but then upon saving, the admin/appearance page displayed the error messages again.