Users cannot access dashboard of subsites & bbpress error

Hi, really hoping someone here can help me with two frustrating problems that I can't seem to get to the bottom of:

1) When a user creates an additional site on my multisite network and they try to access their wp-admin dashboard, they get this message: You do not have sufficient permissions to access this page.

They can access the dashboard of the first site they create without any problems - this issue affects additional blogs that they create. I tried disabling all plugins to see if that helps and it doesnt.

2) When a user creates a new site using this link http://causepages.com/blogs/create/ the site is created but it spews out a whole load of error messages:

Warning: array_keys() [function.array-keys]: The first argument should be an array in /home/pages/public_html/wp-content/plugins/bbpress/includes/core/capabilities.php on line 453

Warning: Invalid argument supplied for foreach() in /home/pages/public_html/wp-content/plugins/bbpress/includes/core/capabilities.php on line 453

Warning: array_keys() [function.array-keys]: The first argument should be an array in /home/pages/public_html/wp-content/plugins/bbpress/includes/core/capabilities.php on line 453

Warning: Invalid argument supplied for foreach() in /home/pages/public_html/wp-content/plugins/bbpress/includes/core/capabilities.php on line 453

Warning: array_keys() [function.array-keys]: The first argument should be an array in /home/pages/public_html/wp-content/plugins/bbpress/includes/core/capabilities.php on line 453

Warning: Invalid argument supplied for foreach() in /home/pages/public_html/wp-content/plugins/bbpress/includes/core/capabilities.php on line 453

Warning: array_keys() [function.array-keys]: The first argument should be an array in /home/pages/public_html/wp-content/plugins/bbpress/includes/core/capabilities.php on line 453

Warning: Invalid argument supplied for foreach() in /home/pages/public_html/wp-content/plugins/bbpress/includes/core/capabilities.php on line 453

Warning: array_keys() [function.array-keys]: The first argument should be an array in /home/pages/public_html/wp-content/plugins/bbpress/includes/core/capabilities.php on line 453

Warning: Invalid argument supplied for foreach() in /home/pages/public_html/wp-content/plugins/bbpress/includes/core/capabilities.php on line 453
Congratulations! You have successfully registered a new site.

I tried re-installing bbpress and WordPress but the issue remains.

Now hoping some lovely person here can help me get my site to work???