Pending from incomplete transaction - Retry fails

Drupal 7
CiviCRM 4.1.1

I have an event setup for registration via Paypal Website Standard.
I have a bunch of registrations Pending from incomplete transaction

Users are saying that if they click cancel at Paypal, they are redirected to the registration page where if they try register again, they encounter an error to do with record already existing.

I've recreated the steps below:

1. Go to Event
2. Click Register
3. Clickthrough all the way to paypal
4. At paypal, click "cancel and return to.. site"
5. I'm redirected back to the registration page (NOT THE EVENT PAGE)
Here, a "Pending from incomplete transaction" status is created for the user"

6. Without going anywhere else, (I'm at the registration form), I click continue (all profile fields filled from previous attempt).
7. I make it to the confirmation page. Click on continue.
8. I then get below Error:

DB Error: already exists

With the following detail:

Database Error Code: Duplicate entry 'civicrm_participant-82-12-6' for key 'UI_line_item_value', 1062
Additional Details:
Array
(
[callback] => Array
(
[0] => CRM_Core_Error
[1] => handle
)

[code] => -5
[message] => DB Error: already exists
[mode] => 16
[debug_info] => INSERT INTO civicrm_line_item (entity_table , entity_id , price_field_id , label , qty , unit_price , line_total , participant_count , price_field_value_id ) VALUES ('civicrm_participant' , 82 , 6 , 'Up to $20,000 a Year -' , 1 , 254.50 , 254.5 , 0 , 12 ) [nativecode=1062 ** Duplicate entry 'civicrm_participant-82-12-6' for key 'UI_line_item_value']
[type] => DB_Error
[user_info] => INSERT INTO civicrm_line_item (entity_table , entity_id , price_field_id , label , qty , unit_price , line_total , participant_count , price_field_value_id ) VALUES ('civicrm_participant' , 82 , 6 , 'Up to $20,000 a Year -' , 1 , 254.50 , 254.5 , 0 , 12 ) [nativecode=1062 ** Duplicate entry 'civicrm_participant-82-12-6' for key 'UI_line_item_value']
[to_string] => [db_error: message="DB Error: already exists" code=-5 mode=callback callback=CRM_Core_Error::handle prefix="" info="INSERT INTO civicrm_line_item (entity_table , entity_id , price_field_id , label , qty , unit_price , line_total , participant_count , price_field_value_id ) VALUES ('civicrm_participant' , 82 , 6 , 'Up to $20,000 a Year -' , 1 , 254.50 , 254.5 , 0 , 12 ) [nativecode=1062 ** Duplicate entry 'civicrm_participant-82-12-6' for key 'UI_line_item_value']"]
)

IF, I now proceed to the event page, I can go through the whole process all the way to cancel at paypal.
It seems I am unable to complete the form immediately I return to the registration page from paypal and need to go to the event page itself (event page refresh?)