HELP! Possible immunohistochemistry contamination! - (Mar/22/2013 )

So our lab suddenly has been having issues with IHC. About a month ago, everything was working fine, but over the last several weeks; we began to notice bright flecks in our fluorescent reactions. Sometimes the fluorescence appears to clump in the tissue and other times it looks very speckled. Along with this, we see poor labeling with antibodies that have been shown in the past to work just fine. I began checking our reagents and found bacterial contamination of our PBS. Unfortunately, someone in our lab contaminated the stock solution and I hadn't noticed. However, we have tried making new PBS, using brand new plates, autoclaving glass vials used for incubating antibodies overnight, etc. But we still can't seem to get our IHC back to normal. I figured the antibodies maybe had contamination so I tried another lab's secondary antibody (thinking our glycerol was contaminated too), but it looked all weird too! Our lab is low on funds so my PI doesn't want to just buy all new antibodies without knowing if they are the problem. Has anyone had something like this happen to their IHC and is the flecked/clumpy secondary a contamination issue or is this something else I am not even thinking about? Any help would be appreciated!

Thanks!

How long have you had the antibodies and how are they stored?