Comment 2 for bug 1362975

I tried to test it ones more.
I discovered, that I was partially right. I really was not able to save the settings with phone number in "invalid" format. It happened first time I entered the phone number consisting of nine digits (i.e. 2112212410 - I was still not able to save it during new testing), but phone numbers in some of the following "longer"formats I might have not tried to save and gave up immediately after the error message "not valid" appeared.
I can confirm the same behavior in all other cases i.e., after saving the record (with phone numbers +420211222410 and 00420211222 for another OU) , if I tried entering a new phone number and saving the record again, the system stopped working. I was probably not patient enough and after some time I tried open the same setting interface ones more again (in the same tab) and I got the error message:

A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete.
Script: chrome://global/content/bindings/general.xml:0