User warning on permissions when submitting step 2 of creating a personal campaign page

After submitting step 2 of create personal campaign page (CRM/PCP/Form/Campaign) I get this user warning:

User warning: Directory /Users/dgg/svn/crm_v4.2/packages/IDS/vendors/htmlpurifier/HTMLPurifier/DefinitionCache/Serializer/HTML not writable, please alter file permissions in HTMLPurifier_DefinitionCache_Serializer->_testPermissions() (line 184 of/Users/dgg/svn/crm_v4.2/packages/IDS/vendors/htmlpurifier/HTMLPurifier/DefinitionCache/Serializer.php).

I've updates files folder to make sure it's writeable - which didn't help. Note that the error indicates that the HTML folder in packages needs to be writeable ????

To recreate

• enable PCP's for Rainforest event
• navigate to 'create pcp' url - http://<your sandbox>/civicrm/contribute/campaign?action=add&reset=1&pageId=3&component=event
• complete supporter profile and continue
• fill in your page info and continue