Can't log time via Zoho Projects API

Can't log time via Zoho Projects API

Hi,

I try to submit and log time into Zoho Projects via API, but get 6500 error:

<response uri="/jsp/error.jsp">
<error>
<code>6500</code>
<message>General Error</message>
</error>
</response>

Here is my HTML file while I try to submit the form:

<html>
<head>
    <title>Zoho add log time</title>
</head>
<body>
<form method="post" action="https://projects.zoho.com/portal/cohesion/api/private/xml/add?apikey=24b8ce1e287712345e4dc5c4f808cf1c&ticket=4a9ef27c9ad89341140dd40a30b1db3b">
ProjectId: <input type="text" name="projId" size="50" value="aca9ba8c0e6b20112e9dbad9c282fc72b882d17df01267ac"><br />
Log Date: <input type="text" name="logdate" value="08-07-2011"> (mm-dd-yyyy)<br />
Log Taskid: <input type="text" name="logtask" size="100" value="Another testing task"><br />
Log Hours: <input type="text" name="loghours" value="8:00"> (ex:0:23, 0:45)<br />
Log Notes: <input type="text" name="lognotes" size="100" value="Another testing notes"><br />
Bill Status: <input type="text" name="billsts" value="Billable"> (Billable / Non Billable)<br />
<input type="submit" value="Add User Timelog">
</form>
</body>
</html>


I can use the SAME apikey and ticket and projectId to get all log time via API. Also I can log on Zoho Projects and log time with the SAME input value via web interface.

Please help. 

Thanks, 
- Terrence