extensions with a cross all over their icons at startup are not corrupted, they are just disabled.
To change this, look for a control panel named like "Extensions on/off" (sorry, I have a german OS version) from which you may turn every single extension and control panel on or off, valid at the next startup.
As to FreePPP, my advice is to do a clean install of the whole FreePPP package, using either v2.5.2 or v2.6.x, but not v2.5.3. Make sure that you remove all old FreePPP files from your extensions and control panels folders (do not forget to remove the FreePPP preferences file!) before installing.
FreePPP 2.5.2 and 2.6 worked very fine with me for years.
[This message has been edited by Walter J. Ferstl (edited 11-22-1999).]