I shall try what you mentioned above. To be more specific on the problem, I have been trying to farm valkyn scoria helmet 3 days now. After many failed attempts due to bad groups, I got to the last boss, when it randomly kicked me to the login screen. When i logged back in, I was at stonefalls, and when i teleported in the dungeon i couldnt join my friends as i was in combat and that meant i couldnt open the door to proceed, which is complete BS as you can join your friends in any other dungeon in the game . Soo, I was stuck in the first room, and when they killed the boss, although i got the achievement, I couldnt get to the boss to loot it, and my friends were unable to trade the set because it appeared as if i didnt kill the boss with them. Then I tried to do the dungeon again, only to get the same issue twice in 30minutes, ruining my run once again. This has happened to pvp as well, and is frustrating, not to mention inexcusable as the game has been out for 2 years+, and such a major issue involving connectivity should be resolved by now.Did you run a repair?
Delete the user settings text file? in case it has become corrupted as a corrupted file can cause the game to crash.
Right click the desk top shortcut. Go into properties, compatibility, tick the box saying 'disable display scaling on high DPI settings'. This was one of the suggestions given to me after submitting a ticket with support after my game started freezing as well as ctd's. Fixed the problem for me.