I'm not quite sure how this little phenomenon is happening but after shooting at 50fps on my 7D and hoping to slow the footage to 23.98fps using Final Cut Pro. I can import the footage fine, render it, then slow it down and it looks fine but in play back it plays for a bit and then the footage halts on a frame yet the audio continues. The footage plays normally the entire way through so I'm perplexed as to why this happens when changing speed.

Can anyone please help?

You need to convert the footage into an editing format. All the DSLR's shoot H264 format which isn't an editing format. Most people are converting the 7D footage into ProRes for FCP but if you check the specific 7D category here on the forum you'll find tons of workflow advice on how to import/transcode/edit your footage properly.

Thanks man, much appreciated. Will sort that out soon.