if you are completely unable to get it to read, can it write to cds? if you can read /write dvds and write cds i would suspect that the read cd diode is gone.
each task gets its own laser. dvd write, dvd read, cd write, cd read each have a separate laser. in the last year or so there have been multiple threads of people who's 2500's have "gone blind" to one or more type of read (dvd, cd) but were still burning flawlessly. you may want to search those threads and see what they found.
i am pretty doubtful that your firmware update killed it. most likely it expired on its own. sorry