Problem using Position() in .NET environment.

Hi,

I'm not sure whether this problem belongs to this group or not. 
But I'm facing very peculiar problem in .Net (version 1.1) environment.

Following XSL works with MSXML4 but NOT with .Net XSL translator:

<xsl:template
match="//input[(_at_)value='go'][preceding-sibling::a[position()=1][contains(
img/@src,'cancel')]]">

<--Do Some operation>

</xsl:template>

When I remove position() from Xpath above, it works.
I'm unable to figure out the problem. If anyone knows the solution, do
let me know.

Thanks,
Animesh