Canon DR-9050c Settings
If you use the default settings, the Canon DR-9050c scanner will hang up when scanning when it runs out of paper and you will be unable to cancel because it is deadlocked due to a problem with Canon's Twain driver. To resolve this issue, you have to change the Feeding Option on the scanner to Standard. This setting is in the Others tab of Canon's Twain UI dialog, as shown in the screen shot below.