Couldn't run a.out

[mashy@hjchoe.kaist.ac.kr]

When i compiled a C program with egcs-2.91.66 i've got the "a.out" file.
The problem is that when i run "a.out" the following error message comes
up

$./a.out
bash:./a.out:permission denied

i checked permission of the file a.out with ls -al

i.e. 
$ls-al a.out
-rwxrwxr-x   1 mashy    mashy       21655 Apr 24 16:14 a.out*

What's the problem? If you have some idea about it, please help me.