problem importing clip into imovie project

I'd really appreciate a bit of advice from you guys. Having recently switched to a mac, I imported some video clips from my old PC and used a program (from the app store) called iVI to convert them to m2ts files. These went into i tunes and will play perfectly through itunes.
The problem is that when I try to drag them into an imovie project (from the music/sound effects option on the right hand side/lower corner of the main imovie screen) it only loads the sound,not the video, onto the project. What is more frustrating is that I did the same thing a couple of weeks ago and it worked fine. Obviously I'm doing something wrong this time but can't think what. Any ideas?
Thanks for your help

You have to import the clips from the drop down menu...you cannot drag and drop into iMovie.

Sorry codda should have said that I've tried that but the clips are greyed out so I can't select them. Will still play on i tunes though.

M2TS (Mpeg-2 Transport Streams) are not an editable format.

You don't say what format the original clips were in, but here's a list of formats iMovie accepts:

iMovie: Using footage from DV and non-DV sources

Convert your files into one of those formats (I use the free MPEG Streamclip for this).