Occasional forms submissions not received

Form is here: http://momondays.com/speak/request-speaking-slot/

This form has a ton of routing set up depending on the city selected by the user. Generally, it works well - but now and then either 1) a user submits a form and goes to our 'Thanks for submitting...' confirmation page, but the form does not show up in the entries (and no notifications are sent) or 2) the form submits, but not all of the notifications go out (each choice of city routes to at least 2 admins, plus the user).

I suspected an Internet Explorer conflict, but I tried in IE and it seems to work. Are there any known issues on this end that would cause either the form to not submit at all, or notifications not to go out?

I'd recommend that you install our logging add-on which can be found here: http://www.gravityhelp.com/downloads/

Install and activate the logging plugin (ignore the message it gives about your license). Then go to the Settings page of Gravity Forms and at the top you will see a Logging link. Click this link and then enable all messages for Gravity Forms Core. Save. Next time the form gets filled out a log will get created. Go back to the Logging page and there will be a link to view the log. Once you are able to replicate this, let us know and we can take a look at the log to see if we can notice anything odd. Once you do, I'd recommend you reach out via a priority support form, which is much quicker and easier for all of us to troubleshoot: http://www.gravityhelp.com/priority-support/

Right on, sounds good.