Uploading .par file won't work immediately

Dear EP friends,

A strange problem.

Uploading .par file won't work immediately ( even after 2 minutes something like that)

Even i tried to clean up the component from the server.

then did uploading.

Only some time it works.

If i restart the server, it won't work.

So again i need to do upload till it works,

Ya i am not modifying the code at all.

What would be the problem.

Please help me out any body.

thanx in advance.

kantha