Unfortunately this is a known critical issue which I have had great difficulty in solving:

https://github.com/matburt/mobileorg-android/issues/22

The workaround in the case of mydisk.se, to say nothing of whether this would be acceptable to you, is to use the non-https version of the mydisk.se webdav system.  This is actually the first I have heard that mydisk's https has issues with Android's certificate system.

I suspect there is some final solution to this problem, but I'm still working on it... I'd recommend adding a note to that bug I just posted above with the details that you have listed here and when I close it (hopefully for the 0.6.0 release) you will be notified of it.

On Tue, May 10, 2011 at 3:31 PM, Robert Goldman <rpgoldman@sift.info> wrote:
On 5/10/11 May 10 -12:34 PM, Matthew Jones wrote:
> Hi Robert... I'm the developer for MobileOrg on Android, we have a known
> issue with self-signed certificates.   What version of MobileOrg are you
> using?  If you visit the site in the Android browser do you get a
> certificate notification also?

Yes, I do, but I get the opportunity to continue through the certificate
notification.

this is android 2.2

Best,
r