My best guess is that it's some type of rounding issue. When you click on the alignment, it's possible to actually move the start point. Maybe you (or someone) else did move it a very minute amount.
Open up the Alignment properties and go to the starting station field, highlight what's there and type in 0.00. This should force it to change. I wouldn't be surprised to find that the ending station changes by that same amount.
EDIT: I just tested this theory. When I moved the start point via grip edit, the new start point remained at 0+00 and the end station changed. So that's not what caused your issue. I did change the start station to -0.001 and the start station now shows as -0+00.
I then did exactly as I previously suggested and it changed back to 0+00.
I'm on C3D 2012.
I tried moving the end point after reading your original post and no luck. Re-drew the alignment and still shows at -0+00. I'm wondering if it's due to it starting where another alignment ends but after I moved it that wasnt the case anymore and it still showed -0+00.
Did you try actually changing the starting station to zero? Change it so that there's nothing but a single zero in the field and hit Ok.
It worked for me. Otherwise, try posting your file.
That's what we want. It should revert to 0+00.00 -- but did you notice the negative is no longer there? I don't see one in your screen shot. Go ahead and press Ok.
Ok. Sorry about that then.
Can you post your dwg file? If it's too large, then you can create a data shortcut to it. Then create a new dwg, reference it in and then promote it -- it'll be part of the new file with nothing else that way.