Thank u all for ur suggestions, I will now try them all one by one.

The rename problem... no, it's actually the underscore character "_" which gets refused, i.e not typed ! And it's not a keymap issue,
cos anywhere else (shell, text editor...) I can type it, but not in the text gadged which opens up upon Rename from Ambient...
My suspect is that they deliberately set up this gadget to reject some charcters not allowed in filenames, resulting in a mess and
not quite the intended behaviour (just my guess).

Oh, I just found another Ambient bug, possibly... when u have a project icon (i.e a text associated with a program) often it doesn't work
the expected way... and this happens apparently on a random basis... when it doesn't work, ambient apparently tries to execute the
text file, issuing "can't start program [name of text file]"... very weird... I really hoped that Ambient was improved a bit since
the old MOS 1.x times but unfortunately it doesn't seem the case... I fear I shall really try out some other desktops...