Accessing actions registered by other plugins

Running Elgg 1.7.3 v 2010071002 - Only one custom plugin running and no core files have been altered. Clean DB.

Background: My new plugin creates a new elgg object called a case after a user fills out the form. The case has user created information on it and is restricted to the user and admins. I am trying to add the ability to upload and attach files to the case. I figured using the built in file plugin would be best, but not sure the best way of going about it.

Issue: I tried basically duplicating the php files and altering some of the variables in order to make sure the plugin redirects correctly and associates the file with the case. It is definitely accessing the action because when you submit the form without a file it gives back specific error messages. However, when a file is selected, it kicks back a "missing ___token or ___ts field" error. I have security tokens in my form per elgg action security standards.

Any suggestions on how to get around this issue? Should I go about this a different way?

Thanks in advance for any help/comments/suggestions!