For your information, I released again Sweet Home 3D 6.5 source code and Windows installer because upgrading to Inno Setup 6 removed support for generated installer under Windows XP and Vista. Therefore, I built again an installer using Inno Setup 5.
As this update didn't modify any other feature of Sweet Home 3D application, I just replaced the existing files hosted at SourceForge.net and updated the V_6_5 tag in source code.

Could the SweetHome3D error/exit-dialog offer an option such as "Should SweetHome3d attempt a restart with the alternative useOffScreen3DView setting?"

I don't like that much this kind of attempt, because you're never sure if you detected the right error and how easy it's possible to launch an other process.

If that's too complicated, would it be possible to add a suggestion or help-link to the exit-dialog.

I had the same idea and it could also be useful for users under Windows which have problems with the 64 bit version of Sweet Home 3D. Pointing to the FAQ could be also a good idea.

I guess the Linux tar could ship with a third startup script like SweetHome3D-Java3D-1_5_2, but called SweetHome3D-useOffScreen3DView

I keep this idea for a future version.