Please allow me a suggestion: There is the obvious possibility that the current PD version cannot cope with 16 projects. Restarting PD after the has crashed may end in another crash when at startup PD attempts to open the last project used. I suggest that you rename or move this last project, so that PD cannot find it anymore.
After that, if PD starts normally, then untick the “automatically load last project” in the preferences/projects? Then look at the project file to see what ever incompatibly issues may be in there. Maybe share that project file here?

Quote Please allow me a suggestion: There is the obvious possibility that the current PD version cannot cope with 16 projects. Restarting PD after the has crashed may end in another crash when at startup PD attempts to open the last project used. I suggest that you rename or move this last project, so that PD cannot find it anymore.
After that, if PD starts normally, then untick the “automatically load last project” in the preferences/projects? Then look at the project file to see what ever incompatibly issues may be in there. Maybe share that project file here?

I have “automatically load last project” deactivated.
When I start PD365 "normal" by double clicking only it crashes after about 2 seconds.

Hmm. Ok. I would in that case completely uninstall PD and install it again. If it has worked before, it should do so again. If not, then it may be good to check drivers, and settings etc.

Quote Hmm. Ok. I would in that case completely uninstall PD and install it again. If it has worked before, it should do so again. If not, then it may be good to check drivers, and settings etc.

Uninstalled and reinstalled twice already.
No success.

PD16 Ultimate still works fine. I can continue with this version but I wanted to try PD365 and I am quite disappointed, also about the very slow official support system.

O dear. Did you work with the trial version of 365?
Maybe an idea to share your DXdiag file with us?

Quote O dear. Did you work with the trial version of 365?
Maybe an idea to share your DXdiag file with us?

No, I subscribed to 365.
Will later share DxDiag here.
Want to get first an official support answer.

OK, fine. I hope that thay will react soon.
Take care
Warry

Quote OK, fine. I hope that thay will react soon.
Take care
Warry

Thanks.

Support reacted by asking me further questions and wanting crash reports and my email address.
I'm a client for many years. They must know my email-address and I submitted dozens of crash reports with my email address.


Update after today's (Oct 21) support answer:

They asked me the same questions again with some additions - not really a big help.

I think my Radeon 5850 is too old for PD365. It was fine up to PD16.
Have ordered a new one from ASUS and will replace it soon.
Hopefully this solves the problem. Will keep you informed.


Update after deinstalling new card ASUS DUAL Radeon RX 5500 XT O8G EVO (Nov. 3)

ASUS support is ultra slow. They could also not say why their GPU did not work.
I personally think it is because it was too new for my older motherboard and CPU.
Here two links:
https://www.pcmasters.de/forum/threads/probleme-mit-amd-radeon-rx-5500-xt.148401/
https://www.techpowerup.com/forums/threads/old-motherboards-new-gpus.227844/

I have ordered another GPU from NVIDIA and will inform soon if this graphics card works.


Update after installing GEFORCE GTX 1660 super Aero ITX (Nov. 5)

Installation of GPU was easy and no problems occured. Re-Installation of PD365 and activation of Hardware acceleration also went through well.

So far all is running fine.

Info for anyone still using old motherboards with Legacy BIOS:

Do not install newer GPUs from AMD/Asus as they require UEFI BIOS.

Installing msi NVIDIA GEFORCE GTX 1660 super AERO ITX worked for me.
These cards must still support Legacy BIOS which I am really happy about.

It is pretty bad that not even the official ASUS support Europe could answer my questions why their GPU does not work with older motherboards.

PD365 works fine now and I hope it stays like this for some time.