Image manager, uploads over 100k never ends

I have a strange issue. When trying to upload images that are more than 100k (appr), I don't get any error messages - but it never uploads.

I've looked in the php.ini, and that says file-upload are some MB.

Any ideas?

This is how it looks like (the circle just keeps swirling beside "Upload":

I have found that this is a server error.

I tried a small image upload script (apart from OC), and I get 500-error (Internal Server Error) as soon as the image is above 100k.

So case is closed for now.