When this happens, I can only recommend that you take the initiative to repair the damage as quickly as possible. The result of not doing so will most likely hinder your performance on every level - with internal and external customers. Let me explain my point with this short, but true, story.
I began working with a lady at a small company years ago. We became fast friends and our families even spent some personal time together. It was normal procedure that I would fill in for this person (who I'll call Debra for this example) when she was on vacation.
One year, Debra left for a holiday completely unprepared. Her paperwork was not organized, the materials she ordered for projects were completely wrong and the specifications she had given to the technicians were also lacking. To say the least, she had left all her coworkers in a predicament.
During the course of Debra's vacation, we discovered that she had used the specifications *I* had created as part of a "test". I knew - and she knew also - that there was a very high probability that the numbers were wrong. I never did find out why she chose to risk using them unless it was due to her haste to leave for a holiday.
Upon Debra's return, she was immediately called into her supervisor's office and reprimanded. Shortly after this event, I began receiving phone calls from fellow employees. They were informing me that Debra was making every effort to blame me for the poor quality of her work.
I went through a variety of emotions from having my feelings hurt to being angry. I simply couldn't believe a friend would do such a thing. I decided I wouldn't mention to Debra that others in the company had informed me of her dealings.
That, however, was my biggest mistake. In hindsight, I can honestly say that I should have gone immediately to Debra and asked if we could discuss her actions.
From that point on, I became increasingly intolerant of Debra. It seemed every minor mistake she made brought forth angry emotions inside me. I was no longer "available" to go to lunch with her. I made sure to walk the other way when I saw her coming. Unfortunately, my behavior towards Debra was being misdirected toward others also.
I began receiving complaints about the way some customers were being treated by me. Had I been projecting my feelings toward Debra onto others? I hoped not, but it appeared that I had.
At that point, I realized things had gone too far. Not only had my "falling out" with Debra caused a chasm to form between the two of us, but it had festered and grown out of proportion.
All human beings operate on an emotional level. In fact, we are more emotional than we are logical. But please take this advice. Don't allow a damaged or broken relationship with a coworker to interfere with the rest of your life.
I have learned this from experience… It is truly easier to overcome a poor relationship with a coworker before it grows and becomes unmanageable than to sit staunchly on your pedestal and spout, "But *I* was right!"