Custom Project Properties SaveAll not working when properties page not active window in VS

Hi,

I have a project properties page for a custom project type that will not save when using the SaveAll command and the properties page isn't the active window in VS 2010. The properties page is derived from a SettingsPage class with is almost identical to one listed in the second post on this previous thread: SettingsPage Class Example. 

I can see through the debugger that the IPropertyPage.Apply function is called when you hit SaveAll and the properties page is the active window in VS. However when not active no call is made to IPropertyPage.Apply. I have also confirmed that the Page is being marked as dirty correctly.

Any ideas what I'm missing? 

Thanks in advance.

Kev