Please tell me what this error message means. Thanks in advance.
I think is occurring when you attempt to make a path using a variable name not in the latents or manifests using a variable name not in the latents or manifests. In this case, a double headed path (S)
"subscript out of bounds" is R's attempt to report this.
If this is the error you're hitting, there's an improved error check in the development trunk, awaiting release. This will tell you what name (perhaps a mispelling) could not be found in the latentVars and manisfestsVars lists.
It sounds like a bug. Can you provide us with a small test case that we can run to reproduce the error?