I have a problem accessing my site (on https) with IEMobile 9 (WP 7.5).
It says it's got problem with the certificate, as if it wasn't valid. Everything works on any other browser or platform I tested (android (several phones and a galaxy tab with stock browser, firefox, opera, dolphin), iOS (iphone and ipad with safari and chrome), an old nokia with symbian, windows 7, linux and mac).
To try to solve this I saved the certificate (.cer) on the server and accessed it from the phone browser. It always complained except when I accessed it through the server IP (192.168.xx.xx). At that point it (said it) installed correctly the certificate. If then I try to access the index.html still using the IP all works fine and it doesn't complain about the certificate. If, though, I try to access the index using the actual URL (blah.myblah.com), it complains again about the certificate, as if it wasn't installed!
It isn't a problem of DNS, cause that's up and serving the right ip, and the phone is correctly setup to use it.
The certificate is signed by geotrust/rapidssl for *.myblah.com.