Alias files turning into unix executables

I'm running Mavericks 10.9.4 and created several alias files pointing to other places on a network-attached storage space. The aliases and their targets are all on the NAS together. When I first created the aliases, they worked as intended, but now that it's about a week later, they have all turned into unix executable files and do not act as aliases anymore. What can I do to turn them back into working aliases?