Second time not recognizing as a function

[thulaseeram]

hi,
i am using the following code for uploading
[HTML]<div id="iframe" name="iframe" style="width:850px; height:120px;">
<iframe name="attach_frame" id="attach_frame" src="http://100.100.100.233/storyclix/upload.php" style="width:850px; height:120px;" frameborder="0"></iframe>
</div>
[/HTML]


[HTML]<div class="form-item" name="_Confirm_buttons" id="_Confirm_buttons">
<input type="button" value="Add media" class="form-submit" onclick="window.parent.attach_frame.upload();" target="attach_frame">
</div>
[/HTML]

when i upload first time it is recognizing as function and uploading successfully, the moment when i try to upload second time it is not recognizing as a function in firefox, but it is working fine in IE. The code that is not recognizing is :: window.parent.attach_frame.upload();
in the above code attach_frame is the iframe name.
plz can any one help me in solving this problem
thanks

[acoder]

What errors do you get?

Can you show the code for the upload?