Quite a bit of reading about Thieves and related matters on my blog list this morning, here, here, and here.
Jim at Carjacked Seraphim starts out talking about the fact that secret DM rolls for searching for traps can really screw the player. While he goes on then to give some new ideas for mechanics to deal with traps, I returned to something I've considered before.
Originally, when the Thief class appeared in the Greyhawk Supplement, they only had a % chance to REMOVE traps. The % to "find" traps is a later addition.
I'm thinking I'll drop the find traps part. If you want to find a trap (whatever class you are), you need to search for it descriptively. Also, as -C and others have pointed out, traps should be telegraphed in at least some fashion to be fair.
Finding traps should be easy, if you take the time to look for them. Removing, disarming, or circumventing traps can and often should be done through roleplay. If no one seems to have a good idea for the roleplay of trap removal or time is pressing, a Thief character can make a roll to see if the PC knows something the player doesn't.
Plus, check out that link to Frank Mentzer's ideas on Thief as a template, rather than a class. Makes Conan and Fafhrd & the Grey Mouser easier to write up for D&D for sure!