Hi zac,
To test if the CPU is indeed the problem...
1. right-click on the chordsheet
2. select 'Song Settings'
3. enable "This song has playback problems... disable fast generation".
4. generate the song
Does it play better?
Explanation regarding the above setting
Normally BIAB starts generating the musical backing and the song starts playing before generation is complete. BIAB then continues to generate the backing in the background while the song is playing. This can strain slower CPUs. By enabling the above option, BIAB is being told to generate the backing fully before starting playback. This means that it will take a little longer for the song to start playing but it should play error free if the problem is CPU related.
Hope this helps,
Noel
EDIT: I see rharv beat me... and with a graphic too!