my adobe reader always worked
now I get "invalid plugin detected"
I am new at this.iam unaware of any changes to the operation of my computer
Assuming you are on a Windows OS box, check the folder: C:\Program Files\Adobe\Reader 9.0\Reader\plug_ins
There were other discussions that referenced the *.api files here. I did not have any of the files that those discussions referenced. So I decied to eliminate the files by date starting with oldest ones. I found one that was dated as of March 2007. Not sure how it got there but I removed it and things worked fine afterwards.
Note that you will need to move the files out of the "plug_ins" folder - putting them into a sub-folder does not work.
Hope this helps.