Hi, I installed LCPDFR last night, and tried to run it this morning and had a similar problem, i.e. that when I clicked it started the load cursor, but then crashed and came up with an error report, denying me access.
Having spent quite a while this morning, reading through this forum and others, I have changed a few things. 1) I have made my GTA4 game folder editable, as it's default is readme.
Do this by going to my computer/ C drive/ program files/ programs files (x86)/ Rockstar games. Now you will see GTA4 game folder, right click and go to properties. At the bottom you'll see some check boxes, the one saying readme will be checked...uncheck it and apply. Wait a second as it'll ask for admin rights, click ok and it'll make the folders subfiles re-writable
Now, when you go to launch the game, go into that game folder and scroll down to "Launch GTAIV" it's the one without the GTA icon, run it as administrator, and it should work (provided you launched the LCDPFR install as admin and have GTA IV patch 1.0.7.0
In my case, I patched the game up after installing LCDPFR and unchecked the readme box in the GTA IV game folder and it ran first time after!
Good luck, hope it all works well.