"Hi, I want to edit some 1080/50i MXF videos from a Sony XDCAM camcorder in Adobe Premiere Pro CS5, but CS5 does like to work with MXF videos. Do you have any ideas of how to get it working?"
As the Sony XDCAM Camcorder records MPEG HD422 codec MXF format, it's not well for editing in Premiere Pro CS3, CS4, CS5, CS6 on Mac, you will encounter importing/video/audio problems when you want to load Sony XDCAM MXF in Premiere Pro CS3, CS4, CS5, CS6 on Mac, the best way is to transcode XDCAM MXF to AVC encoded mov files for that's the most compatible format for Premiere Pro CS5. Come and meet this Pavtube Sony XDCAM MXF Converter, which is capable of converting Sony MXF footage to various video formats on mac.
How to convert Sony XDCAM HD422 MXF to Adobe Premiere Pro CS3, CS4, CS5, CS6 on Mac
Step 1. Connect your Sony XDCAM to mac and keep it on, or use a card reader to transfer your footage to mac. Get this Sony MXF to Adobe Converter installed, click top left two icons to load individual videos or the entire folder correspondingly.

Step 2. Choose best format for editing in Adobe CS5.
Click the drop-down list besides Format, choose Adobe Premiere>MOV(AVC)(*.mov) as the most compatible format as well as best video quality for CS5.

Tips:
You can also choose Apple Prores 422 as the best codec for editing.
And if you want to convert Sony XDCAM to Multi-track Prores, try Pavtube iMixMXF.
Step 3. Adjust output video settings including video size, codec, bitrate, frame rate by clicking Settings, all according to your needs. (Optional)
Step 4. Click the big red circle to start conversion. Wait for a while, you can get the fresh hot converted video which is compatible with Adobe Premiere Pro CS3, CS4, CS5, CS6.
Tips:
1. Click here to learn: How to import Media Files to Premiere Pro on Mac.
2. Refer to here to learn how to work with different model of Sony cameras.
Other realted guides for you:
How to import XDCAM MXF/IMX files into After Effects CS4/CS5/CS6
Edit Sony XDCAM MXF media in Sony Movie Studio Platinum Suite 12
How Can I Convert Sony XDCAM HD422 MXF to Avid MC
Get Sony XDCAM-EX MP4 file to FCP
Ingest Sony XDCAM MXF to iMovie
Transfer Sony XDCAM footage to QuickTime