Daniel,
You're most likely getting this because NTFS permissions to that program files\laserfiche\laserfiche forms directory isn't the only access required. Review my earlier post which details additional access the user account requires.
For example, the HTTP Server API URL ACL rights... to explain, the Laserfiche Forms Routing Service leverages the HTTP Server API to handle it's communications over HTTP (Laserfiche Repository Server does as well, and as such requires similar rights if you're running under a least privileged installation like this).
So when the Forms Routing Service spins up, it registers the URLs (noted in my previous post) with the HTTP Server,... this tells the HTTP Server (the httpsys kernel mode driver) to route requests destined to those URLs over to the Forms Routing Service... and the remainder get routed over to your IIS Web Server. In this fashion, HTTP Server is extended to provide services to not only the IIS Web Service, but any other application (like the Forms Routing Service) that reserves a given URL with the HTTP Server.
But in order for an application to reserve a URL like this, the service account under which it's running must be granted rights to reserve that URL. That's what you're doing with step 3 of my previous post, you're updating the rights for your service account to be able to reserve/register the necessary URLs with the HTTP Server, so those requests will get routed to Forms instead of IIS Web Server.
You're getting the error because the user account hasn't been granted that access, so with the Forms Routing Service spins up and tries to reserve/register those URLs, it fails, and the service shuts down if it can't do this. There are details on this in the application event log, because that's where I found the exact URLs that Forms Routing Service needed to reserve/register.
Most folks run it under local system, or they drop their service account in the local admin group, which would have these rights natively, but it's not secure. So if you're limiting rights to your service account identity, you'll need to add the rights noted in my previous post.