maybe I can help you, piotr-star. Are you talking about media on disc? or the Internet not working. if it's the first one, then maybe your dvd drive needs cleaning or replacing. Try using a cleaning dvd with brushes in it or a good blast of compressed air when the tray is open. If that doesn't work, you may have to shut down your Mac pro, take off the side panel, wiggle out the optical cage, where the dvd drive is, right up at the top, disconnect the power and data cables, take the drive out of the cage (use a No. 1 or No. 0 phillips screw driver), open 'er up, and clean the lens with some ispropanol (100 % rubbing alcohol ) and a q-tip. ) let it dry, close 'er back up, put the drive back in the optical cage, connect the power and data cables (if you have one drive, use the first set of connectors on the cable) and wiggle the optical cage back in, put the side panel back and restart your mac pro. try a disc now-cd, dvd, commercial or homemade. Does it read it? if not, then it may be time for a replacement dvd drive. Any sata dvd drive should work fine and you can replace it yourself. You may need to remove the lip off of the cd/dvd tray before you put it back into your Mac pro. If it's the Internet, I can't help you that much---restart your modem/router, zap the pram on your Mac pro, reset the smc and reboot. If the brand name of your drive is Optiarc then yes, it's probably time for a replacement. If you want to spend the money and time, you can get even get a blu ray drive if you want to, but if not, again, a sata dvd drive should work just fine-don't worry about "Mac compatible", here it doesn't have to be.
JB