When I try to run QuakeLive a Window tries to appear and the .exe crashes.
Here is the warning which seems to be the key to the issue:
$ wine .wine/drive_c/Program\ Files\ \(x86\)/Quake\ Live/Launcher.exe
What he does not understand is how Wine can be built against one version of libpng yet complain that it is using another, older version (which he clearly was asking). Checking with his distribution's package manager shows only libpng-1.6.x and does not indicate that any other version is installed. Thus, the question is how there could be any other version generating this warning message.
I had the same question on my Gentoo Linux system. Portage, my package manager, shows that I have libpng-1.6.8 and only that version installed. So I started looking through /usr/lib and other directories.
I am running a 64-bit system, yet most of the Windows games I play via Wine are 32-bit programs. Therefore, I have a multi-lib system. On Gentoo, there is a package called emul-linux-x86-baselibs that provides a 32-bit libpng (among many others). THAT 32-bit library is version 1.5.15. When Wine runs 32-bit software, it uses the 32-bit libraries.
The 32-bit library Wine finds is older than the libpng-1.6.8 that everything else on my system uses, causing Wine to display that warning message. So far I have simply ignored the warning and haven't experienced any problems.
By being less dismissive we can help fellow users learn more about how and why their systems work. This is a good thing for everyone.
