Create an LTPA Token with SECTOKENGENERATE

I’ve been trying to log a user into notes using SECTOKENGENERATE. I get back an SSO_TOKEN object, but attempting to lock the mhData property causes the following error:

 Thread=[0900:0002-0EB8]

 Stack base=0x0012F420, Stack size = 2216 bytes

 PANIC: LookupHandle: handle out of range

The code I am getting the exception on is:

 pData = (char*)OSMemoryLock(pToken->mhData);

The code I use to generate the token looks like this:

error = SECTokenGenerate(“CN=SERVER/OU=GROUP1/O=GROUP2”, NULL, “LtpaToken”,

"username", NULL, NULL,

&mhToken, 1, NULL);

Has anyone seen this error before? If so, assuming the server is correct and the user exists, what are some possible causes and/or solutions? Any help is appreciated!