System/Test project/Test Specification menus disappeared

[advese]

Writing on behalf of my customer - so I do not currently have access to its testlink server, but here is the story :

Testlink has been installed 3 years ago (Testlink version is V197) ; server configuration hasn't changed
It works perfectly but a few weeks ago, the left frame (System / Test project/ Test Specification menus) has disappeared when logged with the admin (the only role allowed to create project; setup mantis link, ...)

I have checked the Admin profile page, everything seems consistent with another test environment I can access (same check-boxes).

Have you ever seen / faced something equivalent ?
Might you have any clue where to look at, I would be more than happy to hear : corrupted file ? issue with DB ? logs ?

Thank you in advance for your help !

Veronique