Windows Server 2008 R2 does not support hot plugging on certain PCIe ExpressModules. These include:
SG-XPCIE2FCGBE-Q-Z - Sun StorageTek Dual FC Dual GbE HBA Express Module
SG-XPCIE2FCGBE-E-Z - Sun StorageTek Dual FC Dual GbE HBA Express Module
SG-XPCIEFCGBE-Q8-Z - Sun StorageTek Dual 8GB FC Dual GbE HBA Express Module
SG-XPCIEFCGBE-E8-Z - Sun StorageTek Dual 8GB FC Dual GbE HBA Express Module
X7284A-Z - Sun Quad GbE ExpressModule
Workaround
Reboot the system after changing one of these PCIe ExpressModules.