Hi ceath,
I recommend cleaning the Fixing Unit to resolve the issue. Please click HERE for instructions to clean the Fixing Unit.
If the issue continues, take out the toner and rock it 5 or 6 times to evenly distribute the toner. Reinsert the toner then attempt a print job.
If you continue to have difficulties, please contact our support group using the following link:
http://Canon.us/ContactLI