Hi,
I've been using FCPX with my Canon C100 for a couple of years now with no problems (other than FCPX's various flaws).
I import and convert to ProRes in FCPX and then select the footage in the event and change it from 1080i (25psf) to progressive in the settings in the inspector. It has always worked fine.
Today I have imported the footage like always but when I change the footage to progressive it actually makes it look interlaced (obvious interlacing) although the inspector shows 1080p! When I change it back to Upper First it looks progressive although the inspector says it's 1080i. This is the first time it has happened but it is a problem as I have to edit a 30min project and I don't want to get half way through the project only for it to tell me I've edited in interlaced.
Has anyone had a similar problem? Is there a solution?

Try this:
Canon C100 PsF – the fix | Travelling Matt (http://mattdavis.pro/2013/12/30/canon-c100-psf-the-fix/)

Hi Erick, thank for the reply.
That is the technique I usually use. Today, for some reason, it isn't working properly. It's like the PsF footage is already progressive (at least looking at it) although FCPX says it's 1080i. When I use Matt's technique and select progressive (like I always do) the footage becomes interlaced although FCPX says it's 1080p. It's like it's doing the opposite of what it should do and normally does when interpreting footage. Weird and worrying!