To reproduce the problem, log in as a user with the Sales Person role. Make sure the role only has 'Assign' permission on the user level.

Create an opportunity, account or lead. On the form, click the re-assign button and choose another user in the organisation and click Assign.

You will receive the following error:

s:ClientSecLib::AccessCheckEx failed. Returned hr = -2147187962, ObjectID: 91945a03-79c8-e411-80bc-00155d148516, OwnerId: f843d50f-74c8-e411-80bc-00155d148516, OwnerIdType: 8 and CallingUser: 3306bcfa-76c8-e411-80bc-00155d148516. ObjectTypeCode: 1, objectBusinessUnitId: 79b14909-74c8-e411-80bc-00155d148516, AccessRights: 524296 -2147187962SecLib::AccessCheckEx failed. Returned hr = -2147187962, ObjectID: 91945a03-79c8-e411-80bc-00155d148516, OwnerId: f843d50f-74c8-e411-80bc-00155d148516, OwnerIdType: 8 and CallingUser: 3306bcfa-76c8-e411-80bc-00155d148516. ObjectTypeCode: 1, objectBusinessUnitId: 79b14909-74c8-e411-80bc-00155d148516, AccessRights: 524296 2015-03-12T05:31:28.3443903Z-2147187962SecLib::AccessCheckEx failed. Returned hr = -2147187962, ObjectID: 91945a03-79c8-e411-80bc-00155d148516, OwnerId: f843d50f-74c8-e411-80bc-00155d148516, OwnerIdType: 8 and CallingUser: 3306bcfa-76c8-e411-80bc-00155d148516. ObjectTypeCode: 1, objectBusinessUnitId: 79b14909-74c8-e411-80bc-00155d148516, AccessRights: 524296 2015-03-12T05:31:28.3443903Z

Now the weird thing is it's actually re-assigned the record and you don't own it anymore but the error still happens. If you try to assign through the GRID the error does not occur.