In Response To 'Re: Re: some trouble with DSolve'
"gives well known solution
C[t - x/Sqrt[c^2]] + C[t + x/Sqrt[c^2]]"
I think I saw you post this before somewhere.
I worked on your problem for a while.
I usually expect f+C or f*C, where f is some function, results from DSolve when there are not enough initial conditions.
Notice your solution is C[f], where f is some function. If I understand correctly, that means the "solution" is some unknown function C and when you use that unknown function on f then you get the result. I don't recall having seen that before, but I don't have a lot of experience with pde in Mathematica.
I tried introducing conditions one at a time and introducing simpler conditions, all without success.