I have copied all my runtime (poser 5) carefully under poser 6 runtime folder. Opening poser 6 is no problem. All the items are there and seem to work, until a firefly render is wanted. At that moment my processors go to 90% and the computer gets blocked.

Normal render works but gives no good results. re installing did not change the problem. Even the guy at the opening of poser 6 will not render under firefly.

have I done something wrong and what can I do to change it since it used to work well.

Copying is not needed. Poser 6 can manage several runtime folders (just visit your manual).

Did you install the Poser 6 service pak?

Do you know if your hardware drivers are up to date?   I remember that Poser 6 wouldn't render anything for me, until I tracked down an updated driver.

Did you keep you're original P5 Runtime (I hope for your sake you did).
If so then:

Uninstall P6. Make sure that the whole of the P6 directory has gone (delete it if necessary).
(possbly not necessary, but will save you time if it does turn out to be necessary..)

Re-install P6.
Open P6 and go to (any of) the libraries.
Trudge up the arrows til you get to the top. (You'll know you've got there when you see a panel with a big red dot near the top).
There you should find the option to add a different runtime to the existing one.
Click on "add new runtime" (I think that's what it's called), navigate to your P5 runtime and add it.

You should now be able to switch between both...

Cheers,
Diolma