Hello,
I'm using Joomla 2.5.6. and K2 2.5.7. I install the simple image gallery plugin pro 2.5.7. Unfortunately when I try to upload a zip file directly from K2 galleries I get an error that says "There was a problem rendering your image gallery. Please make sure that the folder you are using in the Simple Image Gallery Pro plugin tags exists and contains valid image files. The plugin could not locate the folder: media/k2/galleries/2".
The image path in the plugin is set to media/k2/galleries is that correct?
What I saw is that the folder 2 is created automatically and inside that there is the folder that I had previously zipped. So basically the pictures are inside a subfolder of folder 2.

Any suggestion? Please help me, I'm going nuts here

You should ZIP without the sub directory included.

I'm zipping the folder "A" with no subdirectories and when I try to upload it on sig pro it creates automatically a folder "1" whit the subfolder A inside so the pictures aren't displayed :(

I found my mistake, I was zipping a folder with images inside, instead you need to select the images you want and zip those :)

This error is because you upload the images .zip in K2 before configuring the plugin
Root folder for image galleries -> media/k2/galleries
If you do not do this before you will have error
To correct go to the image folder on the server: root/media/k2/galleries -> delete image folder you uploaded
Then go to the item you have upload image on k2, click on Image gallery tab, click in check-box for delete and click apply or save
Now upload zip image forder and save. That is it.

@tonicosta,
not always. This may be the solution in some cases.