After installing a CRM 4.0 Update Rollup workflows might not publish. The reason may be that the following line is missing from web.config:
<authorizedType Assembly=”mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089″ Namespace=”System.Globalization” TypeName=”CultureInfo” Authorized=”True”/>
If so, then add the line back in. IISRESET is not needed.