Logging into Lion from External Hard drive on MBA!

[vjicecool]

I was unable to boot from external hard drive which is a firewire one. i have a cable from fire wire to USB.
External harddrive has lion in it, when i powered the system on i holded the alt button, i got the chance to load into external HD, when i clicked on the logo. I saw some sign "O" with a line in it.
Any way to solve this guys?

 

[JediMeister]

Is your MacBook Air one that shipped with Lion? If so, compare the build/version number with what you have on the external hard drive. You may find that the build on the external hard drive needs to be updated in order to boot the MacBook Air. If its a 2012 MacBook Air, it may not boot from a drive updated to 10.7.4 because there was a special 10.7.4 build loaded on the 2012 MacBook Airs, Pros.