If Sonar opens to slowly projects or it takes long to display new recorded track it might be that Sonar's picture cash folder is become too full.In that folder Sonar stores images of waveforms that it displays in track view and if it contain too much images of already opened files it can significantly slowdown opening and showing waveforms.So you can check it,and if there is few hundreds or even thousands of .wow files you can delete them all.Folder is usually:

C:\Cakewalk Projects\Picture Cache

or similar.Just search for *.wow files.