thank you. Can you tell me how many images you try to watermark at same time? Usually this number depends on web-server, PHP, the length of path and image-name.
1. A server SHOULD return 414 (Request-URI Too Long) status if a URI is longer than the server can handle. This can be fix with a change in the Apache config file: apache2.conf => LimitRequestLine 65536
2. If you have installed suhosin patch:
suhosin.get.max_value_length = 65536
3. and 4. are a little tricky. all the names of files which should be watermarked are listed in the url. like: C10=file1.jpg&C12=file2.jpg
at the and you can find the path, where the images are stored. It's not easy to shorten this list.
if you have not possibility to change the values for 1 or 2, then you have to watermark partially. 1-20 in first step, 21-40 in second and so on..
I'll try to find a other way to list all the filenames but this is not on the top on my priority to-do list. sorry. but i'll try my best for this.