I have been doing upgrades on APs in our network and one of the AP1200 units had firmware 122-11.JA3 loaded. It would not take the http upgrade, so I loaded 123-4.JA2 via tftp. The file actually made it all of the way onto the Ap without stalling, but it did not finish the process of removing the previous firmware and replacing it with the new tar file.
As of right now, here is the result of a show flash:
2 -rwx 4884480 May 21 2008 14:23:41 c1200-k9w7-tar.123-4.JA2.tar
3 -rwx 1939 May 20 2008 11:50:03 private-config
4 -rwx 5480 May 20 2008 11:50:03 config.txt
5 -rwx 2560 May 21 2008 14:26:47 config.txt.new
6 -rwx 95 May 19 2008 16:49:03 env_vars
7 drwx 320 Jan 01 1970 00:06:48 c1200-k9w7-mx.122-11.JA3
Since the 122-11.JA3 file is a directory I cannot delete it, and I am unsure of the commands to overwrite the old firmware with the new.
And yes, after loading this version, which is the oldest usable firmware available, I will upgrade to 123-8.JEC1. This is just a two step process of upgrading the old firmware.
As you already have the tar file, and can log in to your AP and copy via a tftp server, i would suggest using the archive command to upgrade you AP via tftp rather than copying it to the AP then upgrading it.