When I try to deploy to Central Admin, I get the following message:
<caservername> : http://<caservername>/ : SharePoint Central Administration v3 :
Error: Cannot add the specified assembly to the global assembly cache: SPSolutions.Common.dll.
<caservername>: Error: Cannot add the specified assembly to the global assembly cache: SPSolutions.Common.dll.
his typically occurs due to another process having a lock on the assembly. A lot of times simply retrying to deploy the solution via Central Administration may be successfull. This is done via the Operations tab in Solution Management. If you click on the wsp solution file for Alert Manager, you can deploy to any content Web Application or Central Administration.
If that does not seem to work, try resetting IIS by typing iisreset at a command prompt or via the IIS Management console. You may also try to recycle the Windows SharePoint Services Administration Windows service either via the Computer Management console or by typing Services.msc at Start -> Run.
If all else fails, try rebooting the machine to clear any handles on the assembly.