LSP 2.5 requires NET 4 If I remember correctly, when LSP 2.5 is first installed it should have checked for the presence of NET 4 and offered to download and install it. I do not believe that on subsequent installs that it does this checking. IF installing NET 4 does not work then you could try doing a CLEAN install. If you search over at LSP forums you can get directions on how to do this, but basically you have to uninstall the product - delete the directories and also the dir for LSP in the local/app folder. Under the Program Files you may have both a Graphosx and a Minleon folder since LSP did not delete the former dir when the new 2.5 was installed. the dir under the local/app dir should be called LightshoPro. Do not forget to save any customized items such as the User......xml files if you have 'object', 'paterns', etc... Also before you uninstall LSP save and unload your license to another safe' dir which won't be affected by the uninstall. the dir under 'My Documents' can be left, however, I would also back those up just to be safe.