I have been trying for days to understand why, following an upgrade to Sp2010, none of the statements used in my web part definitions are working. The work fine in SP Designer 2010 and render as before but displaying the web pages in a browser, they do not. What gets rendered appears to use data from the appropriate list (as defined in the web part) but using whatever the last valid stylesheet was rendered, which of course makes no sense. If I remove the import statement completely I get the same result so I can only assume the runtime is unable to find the included stylesheet? I have tried everything I can think of with no luck.
This is a major issue as the only solution I have is to copy all the stylesheet code back into their respective web parts (30+ pf them), which is such a retrograde step.
N.B. I have tried creating a web part page in an empty SP2010 site then putting the XSL template in an external .xsl file and trying to include it but have hit the same issue, so it doesn't appear to be an issue with the migrated site, rather, something in the site configurations of our SP2010 farm?
I would be so grateful for any help available.