My two rescue salukis that I have had for nearly 3 years now after near perfect behaviour off the lead and with other dogs has gone out the window.I have no idea why, they now chase other dogs and always go for biting them, not the throat but down the dogs side as if to bring them down, no serious damage yet, but I now think I may have to muzzle them.
My dog Peggy now tends to lash out even if she is just walking past or if a dog runs up to her.
She recently bit a puppy whippet which was throwing itself at her, where in the past she has always been very tolerent of puppies,I was really upset but luckily the whippets owner was more than understanding.
My other dog dawson hasnt been quite so aggressive but has taken to running up to complete strangers and scaring the hell out of them,but seems to be choosy over who he has a go at.
He also now tries to nip other dogs that he has previously played with for hours.
I really don't want to muzzle, and I am not sure whether they are being over protective with me, if anyone has any advice I would be truly grateful. Ashleigh.

To be honest I have two freinds who have both had Salukis all their lifes and NEVER let them off the lead. They run them in a paddock.

The seem to be a breed that can be a little untrusting of other dogs at times. 

Running along the dogs side as if to bring them down is, I'm afraid, fairly normal sight hound behaviour!  I would say you have been fortunate to have been able to let them off at all really (esp. rescue)
Sarah