jquery validate plugin method/css issue..need help

Move the AmountOther text box into its own <div class="field">

<div class="field" id="radioButtons">
    <label>Please select a donation amount or enter the amount you would like to donate below.</label>
    <div class="option">
        <input name="Amount" type="radio" id="amount25" value="25" class="radio"  />
        <label for="amount25">$25</label>
    </div>
    <div class="option">
        <input name="Amount" type="radio" id="amount50" value="50" class="radio"  />
        <label for="amount50">$50 <span>most popular amount</span></label>
    </div>
    <div class="option">
        <input name="Amount" type="radio" id="amount100" value="100" class="radio"  />
        <label for="amount100">$100</label>
    </div>
    <div class="option">
        <input name="Amount" type="radio" id="amount250" value="250" class="radio"  />
        <label for="amount250">$250</label>
    </div>
    <div class="option">
        <input name="Amount" type="radio" id="other" value="other" class="radio"  />
        <label for="other">other <span>(minimum $1 donation)</span></label>
    </div>
    <div id="donationErrorMsg"></div>
</div>

<div class="field">
    <input type="text" class="textbox" name="AmountOther" id="AmountOther" value="" />.00
</div>

The div that contains the radio buttons is not getting highlighted because that same div contains the AmountOther text field (which is not required if the other radio button is not selected). You have two fields (Amount and AmountOther) in the same div, one is required (Amount) and one is not (AmountOther), there for it is not highlighted.