We recently released a Hotfix for SVS 2.1 SP 2 that resolves an issue with many network drivers not being able to install when an SVS layer is active.  You can download the update from our KB or from our trial-ware portal.  If, for some reason, this doesn't resolve the issue described above please reply to this post with the name of the driver you're trying to install and, if you have a paid support contract, contact support about the issue.