Kirdan

@rupertone: I am as surprised as you are of your discovery, since I have done exactly nothing about the Skype status for last few days. I didn’t even notice the change before you informed me about the fact. It just has mysteriously came back on its own, same way it broke during the weekend.

Although the image came back, the status is invalid (unconnected) as I am online. I think I will wait a little bit more to see if the plugin did fix itself somehow.

EDIT: Well, the backets are not supported as well.

Thanks, smigliorato. Your intuition was great and really helpful. There was something wrong with the filenames. Actually not the brackets, but blank spaces themselves. According to changelog there was a full rework of permalink url structure in ver. 1.8.0 of NextGen gallery, which took place on 12th of June, 2011. Probably from that version blank spaces in filenames were no longer supported. So I just have to rename files as you pointed out.
Thank you very much!