Thanks, Derek. Take a look into sloginfo information after that, it contains a lot of errors, concerning failed to 
render command 0x4E or somthing like this.

> I have filed a PR67213 for investigation, but just to be clear, it is io-
> display that would be preventing the mode switch.
> 
> ________________________________
> 
> From: Mike Gorchak [mailto:community-noreply@qnx.com]
> Sent: Thu 09/04/2009 12:40 AM
> To: photon-graphics
> Subject: Photon can't switch video mode when at least one GLES application is 
> running
> 
> 
> 
> Photon can't switch video mode when at least one GLES application is running, 
> to reproduce this run gf-ph-3d and try to switch video mode resolution or 
> color depth on the same resolution. Ideally AFAIU application should receive 
> EXPOSE event and re-create all GLES stuff, but in practice after attempt of 
> video mode switch, Display Settings utility reports about an unknown error.
> 
> 
> _______________________________________________
> Photon microGUI
> http://community.qnx.com/sf/go/post26482
> 
> 
> 


I have finished the investigation of PR67213.

It is because a hybrid GF/Photon application does a gf_dev_attach(), and io-graphics cannot umount the device, which 
happens during a grafx restart service message.  This is expected behaviour, and part of the architectural compromises 
of GF/Photon co-existance.

Though it is up for debate whether is failing of a mode switch should occur, then reason it happens is now understood.