I´ve got the same problem here like this guy:
I bought my game via Steam and switched it to german language. I am located in Germany. Most sentences from Sam and Max are cut off. The last word(s) is(are) missing very often. Its not real fun to play the games this way. I tried it with 101 and 102 episodes, same error.
I`ve got Windows 7 64 Bit. I did update DX9 manually. I tried to delete the prefs.prop but after that my game starts in windowed mode with a black screen. Alt + Return makes it just a full-black-screen. I had to reacquire the missing prefs.prop to make the game working again.
I updated my sound drivers (which work flawless for any other game) but it doenst affect this problem. Its still there. Whenever i switch to english speech, anything is just perfect. I guess there is a timing problem with the german speech. Its been cut off if its longer than the equivalent english speech.