need to give more information on your computer: INFORMATION REQUIRED WHEN POSTING A QUESTION .
How is your monitor connected? HDMI or DP?
Do you by any chance have the ACER Monitor Driver installed?
Downloaded the TV User Guide. Do you have the TV configured probably for the type of connection you have?
When you try 2560 x 1080 resolution, Play with the Monitor's WIDE MODE and see if it fills the entire screen. Also make sure the Monitor is set for DDC/CI that way the Monitor can be controlled by Catalyst software.