[Plugin: Resize at Upload Plus] Max Image size

Hello – I hope someone can help me. I have a strange problem with the Plug in Resize at Upload Plus. It works very nice in the back end of wordpress. But when Uploading images with a form from the frontend it gives me an error at a filesize of 2,5/3MB or higher.

Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 3648 bytes) in [deleted]/plugins/resize-at-upload-plus/class.resize.php on line 179

Any Ideas?