Forms not working in portrait on iPad

Am stumped! Have just found a very weird anomaly when viewing with an iPad. My forms work fine on a desktop computer and on the iPad in landscape mode but when in portrait mode the fields and buttons cannot be selected.

This form will not work in portrait mode:

• http://ift.tt/1OEaRba

But this one will:

• http://ift.tt/1GMp7h0

Have no idea what might be causing this!!

Any help sorting this out most appreciated.

R