See this thread for more info:
The pertinent info is as follows:
The 2nd Generation Express was introduced mid-June this year, so if you purchased your Express before that time, you either have a 1st Generation Express, or an even older model that did not use the "Generation" nomenclature.
Please check the label on the side of the Express and look for the Model No.
If you have the "old" version, you will see Model No A1084 or A1088.
If you have the 1st Generation Express, the Model No will be A1264.
If you do have the older version of the Express, unfortunately Apple will not allow you to install AirPort Utility 5.6 on your Mountain Lion machine. In other words, the "older" versions of the Express are no longer supported in Mountain Lion.
There are some "unofficial" or "unsupported" ways to do this....with no guarantees....so I am not sure whether you want to contact Apple Support or an Apple Store to see if Apple plans to introduce AirPort Utility 5.6 for Mountain Lion, or whether you want to try an unsupported procedure to see if it might work.
I just ran into this same problem. I have 1 airport extreme and 3 airport express. 2 of which are 802.11g models I use those for air play, and the other I'm trying to figure out how to extend my network, but seem to block all signal when its plugged in.
To answer your question, I went to this address :
Frank has built a free automation to fix our problem. I just tried it, it worked like a champ! Hope this helps your problem. Remember this is not an Apple approved solution, but its free and it worked for me.
I did not offer a "solution" in this thread.
I believe that your your question is referring to a "solution" posted by user kcam1999 in the response above. You might want to direct your question to him with another post.
I have tried Pacifist in the link provided above and it works fine for me. I did not use the "automator." Just drag the extracted AirPort Utility 5.6 application into the Utilities folder on your Mac.
In case anyone else finds this thread and has my issue, figuered I'd log it as well.
I have an old 1st gen Airport Express (looks like a large Mac power supply) which I use to stream music to my stereo by joining my home wifi network. Recently I "upgraded" to a new Xfinity router and needed to re-set up the APE. BUT -- apparently my APE is too old to be managed by Airport Utility 6.1 (which seems like BS, but so be it).
I followed all the instructions re: downloading Airport Utility 5.6, but upon install was told 5.6 is incompatible with My Mac OS (Mtn Lion 10.8.2). What to do now other than buy a newer APE? Sucky suck suck.
Aha -- just dig out of mothballs or borrow any other older Mac (I happened to use an old silver 12" powerbook) and connect it to the APE to with an ethernet cable. Then use the Airport Setup Assistant software which was already on the old Powerbook to set up the APE. I assume you could probably use some other version of APU as well?Once working and reset (green light), I unplugged the APE from the wall and moved it to where I wanted it (behind my stereo cabinet). All set!
Note that even though the APE and Xfinity wifi router were 10 years apart in terms of dates, I had no problem w/ wifi security protocols. I just used the Xf's recommended setting (WPAWPA2PSK-TKIP/AES) and WPA on the APE. Maybe I got lucky, or maybe that Xf setting is universally compatible? Anyway.
So, net net, what I hope I'm contributing here is what to do if you need to reconfig an old APE and run into trouble installing APU 5.6 on your newer Mac. Best of luck.