Why resource from resource file is not loaded properly?

In my application resource file is used for some control like link.Some time that resources from resource file are not loaded properly and that problem occur  for two to three days and later it is working fine even I am not changed single line of code or PC environment.Now I am facing the same issue, I am wondering for the root cause of issue.Please any body know what is cause of the issue and permanent solution also.

Thanks in advance.