OS 10.4 - I've mucked up my keyborad settings!

Hi folks,

My sound volume controls have been suddenly disabled!

Sound is still coming from the line out to the speakers, the slider from the top menu does control the volume, but the keyboard keys won't function.

I was finally using ITunes yesterday and I've obviously changed something and I can't figure it out.

ITunes is ver 7.01, OS is ver 10.4.8

(I can't update to Leopard as Digidesign has not cleared Leopard for ProTools.)

Any ideas?

Thanks in advance, and all the best for 2008!

Jeff