Using contact module - authenticated users now not being logged out.

I recently started to use the contact us module bundled with Drupal. The form works fine but i've noticed some other problems after installing it.

When an authenticated user logs in they can carry out normal functions ok but when it comes to logging out a problem arises, Drupal wont let them log out and they remain stuck, what happens is when a authenticated user clicks log out they are redirected to the logged out page where their username dissapears and turns into a log in button. However if they click log in again they are directed to a page showing them as already logged in from previous log in with one difference, they cannot do anything without receiving error message - "Access denied"

So it seems that authenticated users are not being logged out correctly but all others such as admin are.
The only way around this is to clear the cookies and browsing cache which isn't very convieniant, I think it may have to do with the contact form module but don't know how to fix it.

Also once logged in the 'contact us' link in the user profile area only displays for admin not for authenticated users, this problem may be linked and there may be a permission somewhere (which I cant find) that hasn't been set.

Does anyone have any experience of this?
Thanks in advance for any help offered.