Uploading photos

Does anyone know what would prevent me from uploading photos?
I was uploading without problems until recently.
I removed existing photos to free up storage space.
The max upload is 64MB & these photos are under 2MB.
I’ve tried to use both Browser uploader & multi Loader uploader

Here is the message I receive:
You are using the multi-file uploader. Problems? Try the browser uploader instead.

Maximum upload file size: 64MB. After a file has been uploaded, you can add titles and descriptions.
Crunching…

Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 14976 bytes) in /home/davet01/public_html/davidlthomas.com/blog/wp-content/plugins/watermark-my-image/watermark-my-image.php on line 469