Update: For anyone who experiences this error, unbeknownst to me the computer I was using runs a backup program (Symantec DLO Desktop Agent) that automatically backs up files after any changes, and this conflicted with the SPM preprocessing functions. Once I changed to manual backups the analysis ran smoothly. Definitely a bit of a rookie mistake but I really wanted to make sure no one else found themselves banging their heads against the wall with this error..

All the best,
Jeremy