Would be good if you can check the Baby log via ssh and see if there are any log messages when you get this spinny.

I will probably not be able to do this before Monday, so if you need this urgently, please try yourself.
I'll do it on Monday or Tuesday if the issue is still around by then.

Works for me when connected to Test.sn

Joerg: can you go to Diagnostics and verify everything looks good there when this happens?

Does this happen when pressing the alarm button or navigating via menus

Sorry, I upgraded the firmware today (to 7656) and now I cannot reproduce this.
It happened while navigating through the menus, actually I never noticed the alarm button before you mentioned it now :-)

Could it be that someone fixed it since r7622?
Any chance that there's still a log on the unit?

This was fully reproducible on 7622, even after a reboot.

build 7336 covers alarm and SN, looking at the other changes in the firmware I don't see anything changed from 7620 to 7656 that deals with alarm 

I do see that build 7639 deals with SP > SN communication

I'm glad its working for you, I'll close the bug for now, but if you see it again feel free to reopen and attach the log file.

This bug has been marked as fixed in the 7.4.0 release version of SqueezeBox Server!
    * SqueezeCenter: 28672
    * Squeezebox 2 and 3: 130
    * Transporter: 80
    * Receiver: 65
    * Boom: 50
    * Controller: 7790
    * Radio: 7790  

Please see the Release Notes for all the details: http://wiki.slimdevices.com/index.php/Release_Notes

If you haven't already, please download and install the new version from http://www.logitechsqueezebox.com/support/download-squeezebox-server.html

If you are still experiencing this problem, feel free to reopen the bug with your new comments and we'll have another look.