InfoPath Dev

We have a number of forms with code that have been running in SharePoint 2010 forms services with Sandboxed solutions enabled .   These forms are published to two different site collections.

Out of the blue, SharePoint decided that for just one site collection, it would no longer run the form, giving an error that the custom code in the form cannot be run.  It was also not possible to publish the InfoPath form to the form library presenting an error, again because of the code contained within the form.  The other site collection had no such problem where the form worked ok and publishing was not a problem.

A day later the second site collection exhibited the exact same problem?

To get around this problem we published the form through the administrator-approved template process and the form again worked. Now even doing this has stopped working. Although the fom  can be published and opened in the browser, the following error occurs when calling the SP Get Item web service.

You do not have permissions to access a Web service that provides data required for this form to function correctly.
An entry has been added to the Windows event log of the server.

Any ideas what is going on??

Many thanks

Update

It looks like this problem is nothing to do with sandbox solution. Instead it looks like a problem when trying to access the web services via InfoPath Form Services.  It seems the way form services was trying to access the (Get Item) web service on one web application differed from another.

The error logs were indicating a SSL certificate problem.  

The problem was finally resolved by resetting (switched off and then back on again) that web applications particular application pool.

What caused the problem still remains unsolved but at least a fix has been found.

 Many Thanks