network error ?? newbie question on Access

[p-rat]

I have an application that is located on a shared drive. We are in a
Citrux environment (not an IT guy so not real sure how this all
works). I have two issues that I'm currently trying to figure out.

1. In my Access application I have a main data entry form. I have the
'not in list' code to save an added value to a table ties to a field
on this form. This works fine for myself and one other person in our
home location (I have added values that have been saved to the table
for a couple of weeks now). If the value typed is not in the list
another form opens to where you type the new location and then close
the form to where a textbox asking 'do you want to add this value to
the list' pops up. When clicked, again it works fine for myself and
another user at my location. It seems that for end-users in satellite
offices that if they add a value it saves for that current day, but
then the next day the value is gone from the table.

2. I have reports that all locations can view except for one location.
This person is getting the error "you don't have exlusive access to
the database at this time".

I'm new and don't understand what could be causing these issues. I'm
hoping someone could shed some light on what might be happening.