[TippeX]

can also be a bad image, missing data, safedisc checks like securom, their checks vary in ranges depending on date/time etc.. so a tetchy image may work on 1 day, then not on the next, then 2 days after that and so on... thats what you get for using mini/maxi images... the protection can on occasions check different areas (or even the content / crc of those areas), and on a mini/maxi image the data for those areas may not be correct...

a prime example (albeit, its an old game, but i have fond memories of playing with its check, along with a few other people).. was worms world party.. where, upon connecting to the server a challenge / response style communication was made.. the server asked for the checksum / data from a specific sector (on day #1 it was sector 0x17171717 .. which didn't exist.. but it was a nice tag <team 17 ;p>, then on day #2 they changed it to another sector, varying it as/when they wanted.. so if you had a warez copy you were screwed for playing online)... similar 'tricks' are still in use these days, but not many people notice them...