Multisite Avatar Error

The Multisite Avatar plugin (v. 3.6.1) is giving me an error.

I can upload a photo so it appears on <mysite>/wp-admin/options-general.php?page=blog-avatar&action=upload_process

However, as soon as I click "Crop" I get the error:

Fatal error: Call to undefined function ImageCreateFromjpeg() in <mypath>/wp-content/plugins/avatars/avatars.php on line 549

When trying the Alternate Uploader I cannot even upload it and get the message:

There was an error uploading the file, please try again.There was an error uploading the file, please try again.
Warning: Cannot modify header information - headers already sent by (output started at <mypath>/wp-content/plugins/avatars/avatars.php:484) in <mypath>/wp-includes/option.php on line 568

or

Warning: Cannot modify header information - headers already sent by (output started at <mypath>/wp-content/plugins/avatars/avatars.php:484) in <mypath>/wp-includes/option.php on line 569

Please advise.