Hmm okay. You don't usually have this issue with the USB connected device. Tends to happen more with networked devices.
At this stage I will suggest you try installing the MP630 scanner driver and Canon's MP Navigator scanning application in that order. Note that like the ICA driver, the MP630 scanner driver will install but it won't create a scanner in Printers & Scanners (and you don't need to). It simply copies files to the appropriate folder on the Mac and is required so that you can use MP Navigator (or any other TWAIN based scanning application). With the scanner driver installed and then MP Navigator installed, open the latter (it will reside in Application > Canon Utilities) and you should now be able to scan. Reply if this doesn't work.