GOM player not running video I am trying to run movie on GOM player for Mac, when I open the movie, GOM player name appears on top of menu bar, but no player appears. 

The same .avi file opened well in VLC player. I found out that if there is any other file of same name as .avi but of different extension exist in the folder, GOM player won't run that .avi file. As I have XVZ.avi and XYZ.srt, player didn't opened the file, then I changed the file name to XYZ2.avi. It opened.

What could be the issue?
I'd say it's an issue with GOM Player subtitle renderer. 

It's probably trying to open/read the subtitles but fails and this failure makes it impossible to play the video (it's probably a bug in GOM Player, since most player would just skip the subtitle and play the movie anyway). 

I'd suggest you try another player, VLC is fine, Perian works great with QuickTime or MPlayerX which is free on the Mac App Store. And they all play subtitles, also.