I have made in frontpage several XSLT webparts. Some by selecting list-columns from the data source catalog, some by converting a standard webpart to XSLT-view.

Sometimes (not always!) when I open a page with one or more XSLT webparts, the webpart does not displays the data but, instead displays the message:

"Unable to display this Web Part. To troubleshoot the problem, open this Web page in a Windows SharePoint Services-compatible HTML editor such as FrontPage. If the problem persists, contact your Web server administrator"

If I open the page in frontpage the webparts seem to work ok.
Using another workstation to open the page doesn't help. Neither does refreshing the page.

When I google on the internet I find some published WSS sites with the same problem. (e.g. www.sharepointcustomization.com/.../...gItems.aspx)

Has anyone any ideas about the reason for this?