airport express drops from wifi

As you can see (in picture) I have a curious situation.

Airport Utility can not find my recently re-installed Airport express while I am playing music via iTunes on that same Airport!

NB I am keeping the version of the firmware on 10.5.2 because the newer firmware(s) doesn't give me anything functionality at all.

How can it be that something that worked fine for one or two years now starts getting screwed up because of newer software?

The last 3 versions were plain crap.

Any ideas on what might be the case?

Jeroen