Unfortunately I don't work with Dell hardware very often, so I can't tell you for sure. However, the message is most likely related to drivers which have been replaced in the new image and you may be able to successfully upgrade the host anyway by forcing remediation. To do this enable the checkbox for "Remove installed third-party software that is incompatible with the upgrade, and continue with the remediation" in the upgrade wizard.
André
PS: I removed your duplicate post from the ESXi5 community. Hope that's ok with you.