There is an easier way to fix this problem without having to uninstall .net 4.5.... you have to edit the config file KiesPDLR.exe.config (tipically C:\Program Files\Samsung\Kies\External\FirmwareUpdate\KiesPDLR.exe.config) and remove this line:
...this will force KiesPDLR.exe to use .net framework 2.0
NOTE: make a backup of the file before edit
When trying to update my Samsung Galaxy s2 (at&t), I kept gettting a PDLR has stopped working error. This led to me being unable to update to ics.
I fixed it by uninstalling .net4.5 rc