You fail to mention the operating system you work on.
If you work on a mac, turn off Spotify. It is a known issue - a number of Chrome extensions also cause the same problem.
Adobe's support is quite unable to assist you, because Fireworks was discontinued May 2013, and development and support was halted at that time. Adobe no longer sells Fireworks through their website: FW is incompatible with the latest version of OsX El Capitan, and causes all sorts of problems.
I'm on Windows 8.1 and using an Adobe cloud version of Fireworks CS6
First check if single layer editing mode is turned on.
If that does not work, I believe I read somewhere that the GUI may obstruct selection at times - switch to iconic mode temporarily to see if that is the problem.
If that also does not work, try resetting your preferences