ASP.NET WebServices calling Apartment-Threaded COM Components…

Hanselman’s Weblog
: If you’ve ever had to call a VB6
Component from an ASP.NET (ASMX) XML Web Service, you may (most
probably) get threading errors. In ASP.NET Apps you can mark the
Page directive with “ASPCompat=’true'” but there is not a
equivalent tag for Web Services.