Export Problems in FCP7

Hi guys,

Although I've been editing for a while, I'm still pretty clueless when it comes to the technical side of everything so was wondering if anyone could help me out.

I shot a video using 2 cameras- a Nikon shooting at 23.98fps, and a Canon shooting at 50fps. I'm now editing them into the same timeline, and they playback fine, but every time I try to export, the cuts seem to lag and pixelate. I assumed it was to do with the frame rate, but I have even exported the 23.98fps stuff separately, put it through compressor to make it 50fps and put it back in the timeline, but this has had no positive effect.

Could it equally be something to do with the fact that the files, projects and exports are on a USB hard drive rather than the internal one or a firewire one?

Sorry if this sounds like a stupid question to some of you, but I'd really appreciate some advice.

Thanks!

Mixing frame rates and sizes is not an issue, FCP does that just fine. You're having hardware issues.

Is it USB 2 or USB 3 drive?
What specific Mac model and year are you using?

Also, what GPU and RAM?