The Repair Disk button is greyed out because you can't repair the disk that the Mac is started up from, not safely. If you boot from your OS X installation disc, it'll have an option to start Disk Utility. You can use that to repair the volume.
I'M ON OS 10.4 I'd had problems with blank disks being rejected and wonky uploads on i-photo - so turned to disc utility - on verify it came up with details oF problems like partitions bein and 1HFS being wrong, invalid free volume block - note in disc utlility window says " the underlying task reports failure on exit". The repair button is dimmed so I cannot fix? Any ideas?