Problems with Group By Outline Code

[Michelle]

Hi All,

We have created an project outline code named "Unit". I
was able to group Unit in the open dialog box all along
until last week when all of a sudden it grouped most
projects under a blank value for that outline code. But
I know full well that I had put a specific outline code
for that project and I can see the value under project
information when I go into the project. I have not been
able to figure out what is going on....can anyone give me
some pointers?

Thanks in advance,
Michelle