On a civicrm_webform contribution page, attempting to make a payment gives this error in my Drupal db log:
The CiviCRM "contribution transact" API returned the error: "The file "/tmp/phpZcLm4t" does not exist" when called by function "validate" on line 96 of wf_crm_webform_postprocess.inc with parameters:
Kind of weird? I'm assuming it's something from the payment processor that's being handed down in try/catch blocks, but why payment processing is creating (and failing to find) temporary files is somewhat baffling.
The payment on the form is optional, and I don't get the error when I don't include a payment. I think the validate function bit is a useful clue ...