the other day i went to use my tamron 17-50 f2.8 and found it wasn't working right. it wasn't getting enough light in (very dark) and wasn't able to focus on anything (maybe because of light issue?). my other lenses all work fine, so i know it's the lens.

any ideas on what's happened or what could have caused it? i'm the only one that uses it and it's had no hard knocks or anything that i can think would have affected it. one day it was fine, the next dark.

it's 13 months old, and apparently a grey import (bought it online, didn't even know what that was at the time). because of this the aus tamron warranty repairers won't do warranty repairs (as it wasn't purchased through one of their authorised dealers they don't honour the warranty). the site i bought it off are telling me warranty only goes for 12months and are refusing to cover it, so it looks like i'm going to have to cover the repair cost myself. if it's something major, though, i'm not sure it'd even be worth it.