If SQL Server integration services fails to start. Create a backup of DTExec.exe.config and MsDtsSrvr.exe.config file  in   “C:\Program Files\Microsoft SQL Server\90\DTS\Binn” and add  <generatePublisherEvidence enabled=”false”/> under runtime tag and the start the SSIS service.

Here is an example DTExec.exe.config file for SSIS 2005:
<configuration>
<startup>
<requiredRuntime version=”v2.0.50727″/>
</startup>
<runtime>
<generatePublisherEvidence enabled=”false”/>
</runtime>
</configuration>

Here is an example msdtssrvr.exe.config file for SSIS 2005:
<?xml version=”1.0″ encoding=”utf-8″ ?>
<configuration>
  <runtime>
    <gcServer enabled=”true”/>
    <generatePublisherEvidence enabled=”false”/>
  </runtime>
  <system.diagnostics>
    <switches>
      <add name=”TraceClientConnections” value=”0″ />
      <add name=”TraceManagementCalls” value=”0″ />
      <add name=”ServerTraceSwitch” value=”0″ />
    </switches>
  </system.diagnostics>
</configuration>

More details about the above tab is mentioned in http://blogs.msdn.com/b/amolravande/archive/2008/07/20/startup-performance-disable-the-generatepublisherevidence-property.aspx