user29677: I made a double payment to the same address mistakenly since my internet was a bit slow, and one payment has 8 confirmations. The recipient says he hasn't received it. I got this message from the transaction: 

A conflicting transaction has been detected in our memory pool. The transaction hash displayed below may change.

What can I do to resolve this?

user15492: A double spend is not possible. A double spend attempt, yes. You might try and (accidentally or intentionally) broadcast two different transactions that spend the same bitcoins. But only one will eventually get included in a block.
If you say one payment has 8 confirmations, then that's the one that became final ('set in stone') and the other will never happen.

29677: <p>I made a double payment to the same address mistakenly since my internet was a bit slow, and one payment has 8 confirmations. The recipient says he hasn't received it. I got this message from the transaction: </p>

<blockquote>
  <p>A conflicting transaction has been detected in our memory pool. The transaction hash displayed below may change.</p>
</blockquote>

<p>What can I do to resolve this?</p>
 15492: <p>A double spend is not possible. A double spend <em>attempt</em>, yes. You might try and (accidentally or intentionally) broadcast two different transactions that spend the same bitcoins. But only one will eventually get included in a block.</p>

<p>If you say one payment has 8 confirmations, then that's the one that became final ('set in stone') and the other will never happen.</p>
