struts problem - html:form tag inside logic:iterate

Hello. 

I have a problem with <html:form> tag that is inside <logic:iterate> tag.
Here is code sinppet:

<table>
<logic:iterate id="searchElement" name="SviArt" property="listaArtikala" 
scope="session">


<tr>
<html:form action="/dodajBasket" method="POST">                                 
          
  <td width=10%>
    <html:text property="narucenaKol"/>                                         
  </td>
  <td width=5%>
    <html:image src="/skladiste/images/basket.gif" onclick="submit();" />
  </td>
  <input type="hidden" name="idArt" value="<bean:write name="searchElement"
property="idArt"/>">
</html:form>
</tr>

</logic:iterate>
</table>                                        

I have some ordering system and I get informations about products from database.
Then I put those values in the session and I show them in table. In that thable
I have input field where user can write amonut of product he wants to order.


In the next action I get idArt (in hidden value) and I add amount of that 
particular
product in some sum of amounts.
I have image to submite this form (insted of button). 

My problem is that sometimes when I click the submit image (for one product)
 form submits twice, so I got wrong sum of amount (like I order twice as much
of the same product). Real ugly part of that problem is that it appears random.
Sometimes form submits once (as it should be - about 65% cases), but sometimes
(35% cases) it works wrong. In debbug mode I saw that two same threads are 
generated
(I said, in some cases).

What could be the problem?
Please, help.

Sasa