All developers face this at some point: your software somehow just refuses to work on the customer's computer, BUT it does work fine on yours. You spend hours, days, weeks trying to figure out whats wrong and, eventually, go crazy. Especially after you have tested your software in Firefox, Chrome, IE7, IE8, Safari and even the freaking IE6 and Opera - but you still can't reproduce that freaking bug, that the customer reports.
That's when you get desperate and your only option is to use TeamViewer or some similar remote-desktop software.
I have recently found a handy solution - showmewhatswrong.com. It's a great web-application that generates a special link that you can email to your user. This link, when opened by a user, launches a browser extension and records a screencast of what is actually happening on the user's computer and sends a flash video back to you afterwards.
I just tested this with an actual customer of ours (thanks, Al!) and it works. Awesome.
Too bad they do not offer commercial use for this tool, otherwise I'd be happy to integrate this into our web-based help-desk software. Sent them a request couple of weeks ago - no response...
P.S. Actually I've twitted about this tool not so long ago, another reason to follow me if you don't.