500 Internal Error on Verizon 3G/4G only

See more:

HTML5

ASHX

PhoneGap

We have a Phonegap application (HTML5 front UI) running for iOS. This uses a ASP.Net Handler set for the business logic.

I am stuck with a wierd issue from past few days.

The user is complaining that he gets a "Internal Error 500" when trying to navigate through various screens. Not consistent for a single screen.

We have localized this issue to be occuring only on Verizon cellular network and not other network (AT&T works beautifully).

The application uses a simple AJAX post and calls the ASP.Net Handler for data and the ASP.Net handler returns the data as JSON.

My Questions -
1. What should I look out for regarding the error ? (Event logs, server logs etc ?)
2. How do I catch the Internal Error 500 and may be look at whats happening ?

Any inputs are welcome.