BUG #5545: permission denied on delete

The following bug has been logged online:

Bug reference:      5545
Logged by:          Niranjan Pandit
Email address:      smartnp81@gmail.com
PostgreSQL version: 8.4
Operating system:   Fedora 13
Description:        permission denied on delete
Details:

role A is member of role B, role B has delete privilege also the select
privilege on the id field of the table. when logged in with role A and set
role to B, the permission is still denied to delete a record, any ideas why
is permission denied ?

the set role is in a security invoker function before the delete statement.
Could this be related in anyway ?