AC ignores doesn't process attachments. I have a feeling that you are trying to capture a big piece of text from body and thats why it fails. Check your "Capture rules", if it don't help please expand logging, reproduce it one more and attach logs here.
How to expand logs:
Don't forget to restart.
On the Capture Object tab, I had chosen to use the Body of the message and all of the text that I find there. The email that I was alerting on had an html email which was most likely causing the storage SQL error. Thank you for your assistance.