strange xsl security exception under asp.net

[Brian Spanton]

hey all,

if anyone has any info on the following (or any
experiments to suggest), i'd be grateful. i'm at a
complete loss.

exception:

Message: Invalid Xml.
Class: class System.ArgumentException
Stack:
at System.Security.Policy.PolicyStatement.FromXml
(SecurityElement et, PolicyLevel level)
at System.Security.Policy.PolicyLevel.CheckCache(Int32
count, Char[] serializedEvidence, Boolean& xmlError)
at System.Security.Policy.PolicyLevel.Resolve(Evidence
evidence, Int32 count, Char[] serializedEvidence)
at System.Security.PolicyManager.Resolve(Evidence
evidence, PermissionSet request)
at System.Security.SecurityManager.ResolvePolicy
(Evidence evidence)
at System.Xml.Xsl.Compiler.Compile(NavigatorInput
input, XmlResolver xmlResolver, Evidence evidence)
at System.Xml.Xsl.XslTransform.Compile(XPathNavigator
stylesheet, XmlResolver resolver, Evidence evidence)
at System.Xml.Xsl.XslTransform.Load(String url,
XmlResolver resolver)
at System.Xml.Xsl.XslTransform.Load(String url)

xsl file contents (any more than this changes nothing,
any less gets normal and expected xsl compile errors):

<xsl:stylesheet
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
</xsl:stylesheet>

notes:
1) framework 1.1, xp pro
2) asp.net app written in j#
3) url from bottom frame is a file path to a local xsl
file
4) this code path and stylesheet declaration work fine
for hundreds of other xsl files
5) one specific file that hasn't changed in months just
started throwing this exception
6) contents of the file do get parsed to a point, but
have little to do with it (see above)
7) the same thing happened to one of my coworkers a few
weeks ago but with a different file, it hasn't gone away
8) resetting iis or rebooting machine doesn't help
9) deleting and recreating the file doesn't help
10) same code path in a console app works fine
11) blowing away
C:\WINDOWS\Microsoft.NET\Framework\*\Temporary ASP.NET
Files\[My App] doesn't help
12) only workaround appears to be to rename the file

any ideas are much appreciated.

thanks,
brian