Okay, let's go back to some basics here (best thing to do usually)
1. Check to make sure you are basing the report on the correct table or query.
2. Check to make sure your query/table (I always recommend using queries) has three separate fields for city, state, & zip
3. Make sure the names of those fields in the query/table MATCH exactly the names in the report, right down to spaces.
4. Verify that you are not using data from an OLD database such as data stored under access 95/97 and now being run with a copy of access 2003. (or even 2002/2003). If memory serves, the "Trim" function went the way of the dodo bird recently.
5. If you're using data from an older db with a newer version right now, go to this site:
http://support.microsoft.com/default.aspx?scid=kb;en-us;283166&Product=acc6. I personally recommend option 2 as it's easier and takes care of other problems that might crop up.
If this doesn't help...I have the following questions:
1. Where did this data come from and how was it brought into access?
2. What version of access are you using?
3. what are the field properties of the field in question?
Let's see what good this does!