Hi, I have a large model in Excel Services that I have been using from Infopath Forms Service also.
One of the previous comments could be true that there is a security issue due to the double hop authentication, although, we do NOT have Kerberos in our environment.
I noticed on one of my forms, I could NOT get the form to work as a browser enabled form even though it looked like I had everything correct on my form!
I actually recreated the whole form again, from scratch and now it works in the browser! (A test form screen shot using my Excel model is attached)
The only difference, I believe, was that when I created the first form I used 'Blank Form' as the template, and on the second go I used 'SharePoint Form Library' template!! Go figure!!
Oh, yes and every web services call EXCEPT 'CloseWorkbook' work, yet, I can call OpenWorkbook as many times as I like and get a different session id returned, which is strange.
On my form I am actually passing in ~ 60 parameters (about 10 years of financial data) using a single string, the Excel model splits the string up and populates the model. I have roughly another ~100-120 named ranges in the model that I then extract.
I would suggest creating a test form similar to the one attached to check out that you can actually achieve this in your environment.
I'm more than happy to create a blog/video explaining how to do this similar to Hilary Stoupa's Excel REST connection method if anyone is interested?
Cheers
