power steering problems ?

[sneezys72]

About a month ago I replaced the input shaft seal. I had to take the adjuster plug out to do it. The worm gear came out at the same time. I got it all back together and everything has been fine. Leak has been fixed and sterring was fine. Today I was driving (at slow speeds luckily), and the steering box locked up. It took a couple of tries to turn then it loosened up and was fine. I drov it home and it did it again. Any idea what this might be? I don't think the pump is out. It's not like losing power sterring, it won't turn at all when this happens. Thx for the help.