[Plugin: OptionTree] Stylesheet suddenly missing

Hi,
Does anyone have any idea why the stylesheet for Option-Tree plugin would suddenly no longer be there?
I have to use Option-Tree to get the Purity theme to work. It was working fine for months with version 1.1.8.1 then suddenly broke – have not changed anything. Am running WP 3.4.1 but it was fine on this version until today.
Have upgraded Option-Tree to current release but it still reports this issue.
All the customisation is in there still, in Option-Tree. It just doesn’t seem to want to talk to Purity anymore.
Any help appreciated!
Richard

http://wordpress.org/extend/plugins/option-tree/