Way to execute a command from CLI

OS : Linux
Kernel ver : 2.6x

Is there any legit difference between way that shell interprets the below mentioned command lines in Linux environment?

Option A> . <exec_file_name> arg1 agr2
 
Option B> ./<exec_file_name> arg1 agr2

The reason for me asking this silly question is when I try to execute a simple Korn shell script using these two command lines , it runs fine . On the other hand, when I try them on a third party utility , the first option aborts with an error like "Cannot execute a binary file...." , but the second option executes the file successfully.

Can someone please help me to understabd this issue ?

Regards
Kumarjit.

Option A sources the command, executing it in the current shell.
Option B executes the command in a subshell.

Of course, if you try to source a binary it'll fail.
But even scripts can act quite diffrently whether upon they were sourced or executed.