We use a script to just kill "sdclient.exe" to resolve this error. Sometimes we also delete the entire packages folder or the folder for that particular task (under the Packages folder).
REMEXEC1= cmd /c taskkill /F /IM sdclient.exe
REMEXEC1=cmd /c rmdir /s /q "C:\Program Files (x86)\LANDesk\LDClient\sdmcache\packages"
This help me a lot...