For the JFBC 4.1 or 4.2 release, we're planning to implement the new requests system (and replace our JFBCInvite module), but haven't scoped out which release that will be in. Additionally, I haven't done a huge amount of research into it yet... but will help where I can.
First, the FB.provide function can be thrown off a few ways we've seen in the past. Check for these problems:
1) You don't have any other scripts including the all.js Facebook library. JFBConnect is usually tolerant to other inclusions, but some functions in the Facebook library can really go crazy if that library is included twice on the page.
2) Make sure you're not including any of the other Facebook libraries on the page, especially the Share button in any form.
Next, for the 'new' requests, in your Facebook application, in the Info->Advanced tab, there's a "Migrations" section. One of the settings here is for "Use Requests 2.0", or something similar. I believe that needs to be enabled.
Looking through the docs for the apprequests API:
developers.facebook.com/docs/reference/dialogs/requests/
The only thing I see wrong with your function call is that the to: to should be in quotes. Since that parameter can accept IDs or usernames.. I think passing it in without quotes may be causing the function problems. Also, I'd recommend alerting out the ID of the user, just to make sure it's being passed into that function properly.
Hope that helps, and definitely let us know how that goes. Again, we're planning some robust support for the Invitations in an upcoming release, so you're feedback on implementing it would be great to hear!
Thanks,
Alex