Hi Milan, this problem starts when you upgrade opera to latest version?
try to upload a video in MP4 or MOV format for "Only me" share settings to see if he uploading.
for freeze tabs try to clear %temp% files in your pc.
I tried here upload a simple video with opera Stable and my video is uploaded ..
In Otherwise be sure to Opera Turbo is in OFF (that's important)
I tried both mp4 and mov files, and both doesn't work in opera, while both work at the same time in firefox.
Opera TURBO is disabled.