I don't know if you are interested, but . .. . I just did some research over at SONY and Vegas 7 is now up to V7e! You have V7b. Now in V7c, there was a "fix" to crossafades as a result of a "rounding issue" - that sounds like maths to me and as such if you ARE employing some FXs and this "issue" is still remaining within your release, then maybe you might wish to consider updating directly from SONY site? Up to you. If it doesn't work, then at least we would know that THAT wasn't the issue here. However, there is a whole load of fixes you ARE missing out on! You are on "b" it is now up to "e".

Cheers,

Grazie