How do you as GM deal with failed checks that have to be successes in order to continue with the story. For example, the PC's have to hack the average computer check in order to open up the looked door that leads to the prisoner you have to free. "OK I rolled my check and failed, and I roll again, failed. Again, failed... again, finally!" Do you just let someone role until they succeed (of course after adding the various advantages and threats involved which each role, which I guess could help or hinder the success rate)?
What are you thoughts on this? What would you do/how do you handle situations such as this?
Thanks!