I am using my iPhone application on my iPhone 3G OS 3.0.1 without any problems. The application connects to an API URL at https://api.serverdensity.com/1.0/ and all requests go through it.
A user of the app has reported that they are now suddenly getting an error "untrusted server certificate". No other users are experiencing this issue (that I'm aware of) and I cannot reproduce it.
The SSL certificate is a wildcard certificate on *.serverdensity.com. It is purchased from GoDaddy and is valid until May 2010.
Further, the user is running OS 3.0.1, the time/date are set correctly on the device and if he visits the API URL in Safari, it loads up correctly.
Any suggestions for the cause of this?