problem filtering on grid

Hello,

On Dynamics AX 2009 ...

Everytime I open a grid, that has user id on it (such as administration + users), and trying filtering the field : user id, I run into a problem:

*ei*, will fiter nicely (with "Eitan" line for user).

*eit* will filter nicely,

but if I filter *eita* - no record match.

It will no filter fields start with *eita*, but meital found.

This strange behaviour happens only on several environment, but not at all of them

This happens also for other filtering on other "User Id".

What may be the problem?

Thanks :)