Invalid image dimensions

Hello

From gallery site I choose Manage pictures and Resynch Gallery
What could rise this error?
In folder is only one jpeg file. I replaced bigger one with smaller and then with a very small jpeg file. Error is the same. I run modx from virtual PC.

PHP error debug
Error: imagecreatetruecolor() [function.imagecreatetruecolor]: Invalid image dimensions
Error type/ Nr.: Warning - 2
File: C:\AppServ\www\assets\snippets\maxigallery\watermark\Thumbnail.class.php
Line: 359
Line 359 source: $this->img["des"] = ImageCreateTrueColor($X_des,$Y_des);

have you been able to upload any images yet? is GD installed in your server environment? you can check it from phpinfo.