• When you say "some" users, is this a few or a significant percentage of the user base?
• When did this start happening, and what changes occurred just before?
• When you say Notes starts in an old design, do you mean the mail file opens with old design or that Notes itself opens in an old design (i.e. Basic mode)?
• Is Notes crashing? Check the IBM_TECHNICAL_SUPPORT directory to see if nsd* logs are being generated when this occurs.
• Do you have auto-save enabled? Check File -> Preferences -> Basic Notes Client Configuration.

• This is a little percentage of the user base, though there are always an x percentage which doesnt report the incident.  With some I count around the 3 to 6 form an userbase of + - 400 users.
• We moved from Notes 8.5 to notes 9.0.1, after that the problems happened for the user. The windows platform is 8.1, the notes application is ibm notes 9.0.1 and the design version is yet 8.5
• From the start screen you can see that notes is starting in an old design, when it opens then it is in an old design. Dont know if this is the basic mode though.
• I checked the logs and  even send those to our coleague IT department. There are much errors in it though dont know to which part I need to search for
• Auto save is automaticlly disabled and the user itself needs to enable it.

Really thanks for the usefull questions and short explanations.

I run eclipse notes but occasionally notes just starts up in basic mode. Ive noticed it sometimes has an added window displaying "bookmarks" Iin the title bar, and a single "databases" tab from the start menu bookmarks.

I close notes, watch nlnotes leave the process list on Tasks window, restart. Notes relaunches, goes back to eclipse.

De-install notes completely

Delete notes

Deactivate Virus scanner (temporarly for exclusion test, make sure no external websites can be used using a proxy web block)

Restart computer

Re-instal Notes 9.0.1 FP2 Multiuser (Not FP3)

Still with virus scanner disabled start notes using a User who does not have stability issues (different mail file, settings, policies, ID)

Run your tests.

If it crashes check user access rights on OS.

If it doesn´t crash, activate the virus scanner and restart the computer and do tests again, if it crashes check you virus scanner exception list.

If it now works, then switch users to the instable user and run tests again, One of the following would be at fault. (Mail file, settings, policies, plugin.)

If it crashes than look for a file with nsd...... in it's name in the folder "IBM\Notes\Data\IBM_TECHNICAL_SUPPORT", and send it to your admin our IBM Support Partner.

If it's the installation, it's in all installations. 

In my case I can also assure, it's Notes basic. I've checked the version window, & I've worked inside the odd environment for a half hour or so in emergencies.

All that said, it may not be the originator's problem. In earlier versions of Notes I'm also aware of another cause: if older Notes DLLs are inserted in  the path Notes may try to use them.