If you select an image in ProSelect and do an Control-Y (PC) or Command-Y (Mac) then the RAW file associated with the currently selected image will open in Photoshop or Lightroom. If not, then check the following:

1. Preferences -> Importing Images ->Link Bypass RAW files is checked and you have the raw file extension entered in the boxes below this.
2. Preferences -> General Settings -> General -> Photo Editor -> Default Raw File Editor is set to the editor of your choice.
3. A Raw image of the same name as the selected image is in the same folder as the selected image. You can check the location of the imported image by selecting it and doing a Show Image Info (under the Album menu).

If using Lightroom 3 or 4, please see this article for important information.

UPDATE MAY 2014

It when choosing "Open Selected RAW image in Lightroom... " in ProSelect an error window comes up saying "Sorry there was problem, Could not find any RAW files for image: [filename]", then the following may resolve this for you.

We have discovered another area within the metadata that will actually change the file name upon export.

If you are using presets to automatically add metadata like copyright information to your files, the "Copy Name" field must be empty or the text used will be added to the filename of the exported images from Lightroom, therefore, loosing the links to the original raw files.