Mac isn't picking up guitar&mic. help!?

[HarryBB]

GarageBand and Logic pro are not picking up my guitar, iv got the istudio monster lead from apple plugged into the sound input jack of my mac and it is not picking up the signal, it was perfectly until a week ago, now it just clicks. thats the only sound it gets, and i have no idea where they are coming from. just some strange clicks and no guitar or mic.
iv also tried not using the istudio lead and just the mic into my mac and its still not getting it.
Pleassssee Help!
i recorded a video of it, YouTube- GarageBand and Logic Pro not picking up my guitar signal , Help!?!
my guitar was plugged in (sorry theres no sound) and you can see the sound bar thing just going up and down, its just a continuous clicking that only happens when somethings plugged into input.
thanks.

[Steve Conner]

Sounds like the audio drivers on your Mac are foobar'd. Maybe your local Apple store could help?

[TerryEncore65]

Do you have something like an "IMic" its a little gizmo that gives you a "line in" connection through your USB port. It's made by Griffin. It accepts mic and line inputs.