XML xlst mystery

OK, so I have done a little XML and can import material from simple feeds. I have a few apps I have written and they run fine. I paste the feed, select the style sheet, and import. No problem.

Starting last Thursday, I began a new file for a new project and I needed some RSS imports so I did as I always do, I copied a stylesheet that works, checked the tables just to make sure the field names line up, closed the sheet, pasted the RRS address into the import, selected the sheet and this is where the problem started.

When I went to Specify Import order, FileMaker begins to send up a error that:

"XSLT Warning: Fatal Error at(file , line 0, column 0) An exception has occured! Type:RuntimeException, Message:The primary document entity coulb not be opened. Id=file:///..."

I started poking around and trying again, moved the sheet to a different folder, renamed it, nothing. Checked the error online and nothing useful.

Now, the really odd thing is that when I try with an old style sheet that worked in the past for another file, it works just fine, but anything new simply will not allow me get around the error. I checked my folder options and they appear to not inhibit any file use, and the file properties as well. I am stumped.

What can be the issue that keeps the XML parser from using a copied style sheet that has no difference from the working original from functioning? Any help would be greatly appreciated. Thanks.