I can't enable my web proxy since it says disk is unformatted and if i click format disk, it says - Cannot format disk unkown drive (4)

i'm running a 2.8.17 that was running fine until i upgraded to 2.9.4 and could not get my policy based routing to work, then i reverted back to 2.8.17 and suddenly web proxy was broken..

any ideas??

Give more info, is it a PC or RouterBoard? If it's a PC, I suggest using a seperate harddrive for cache, and format it using the webproxy format function...