I have installed the SSL package from Sebastien and enabled all 3 Security features.
If I try to add my custom form url under the list of ssl required paths in setting, it no more work, generating an infinite redirection loop.
Removing it from the list make it working again.
I suspected the recaptcha in a frist try but after removing it, no improvment.
My custom form is basic, it uses only classic fields, no 'specials' elements.
I will try to have a look in code, but if anybody has some advice, it's welcome.