ECMerge is built as a 32 bit executable for Linux, it means that on 64 bits Linux you need the 32 bits proxies for 64 libraries, in particular those of GLIB and GTK.
When those proxies are not installed, the following message appears (when launching from command line):
/opt/elliecomputing/ecmerge/guimerge: relocation error: /opt/elliecomputing/ecmerge/guimerge: undefined symbol: g_atomic_int_add
On Debian based Linux (Debian, CentOS, (K)Ubuntu...), use synaptic or apt-get and install the packages: ia32-libs, ia32-libs-gtk (needs 'universe' distrib).
On Fedora 64 bits, it seems that RPM packages are already installed (for IA32EL). Please submit a ticket, if you have a problem | 
