would seem like your laser is going bad.. or, the RW is a cheap brand? but yeah all standard DVD drives, can read RW media, they just can't WRITE to it.. lol..
the only other thing i could think of, is type of media, as some people will think dvd-RAM disc is the same as dvd-r lol.. and other stuff.. but this prolly isnt the case with you..
but yeah, if you aren't having a problem reading any type of other disc, meaning no slow loading times or failure to load other types of discs, then you have to assume it is the RW disc that is faulty mate..