Problem with uninstalling via SW Installer UI client

Anyone have experience with "Uninstall" using SwiUI::RSWInstLauncher? For all my tests, the Uninstall method returns -1 for what I believe are valid parameters. Here's a summary of the code, and what I'm trying to accomplish:

...
RApaLsSession apa;
apa.Connect();
TInt status = apa.GetAllApps();
if (status == KErrNone)
{
TApaAppInfo aInfo;
while (status == KErrNone)
{
status = apa.GetNextApp(aInfo);
if (status == KErrNone)
{
if (appname.Compare(aInfo.iCaption) == 0)
{
SwiUI::RSWInstLauncher iLauncher;
int error = iLauncher.Connect();

error = iLauncher.Uninstall(aInfo.iUid,SwiUI::KJavaMIMEType);
if (error != KErrNone)
logger.WriteFormat(_L("Failed to KJavaMIMEType: %d"), error);

iLauncher.Close();
break;
}
}
}
}
...

It's also worth noting that I've tried every possible MME type available in SwiUI, and in all cases it returns the same result "-1". For some of the MIME types, it displays something like "Remove failed". I'm assuming that's because the MIME type was wrong, although it's curious that it only complained for 2 of the types for a test application that is actually a JAVA application.

Any insight would be appreciated.

Tim