is there a limit as to the number of entries a combobox can contain running on a form?

I have the following scenario:
1. customer table has 100 customer entries
2. running an APP, open form "Invoice Entry", form contains a combobox with rowsourcetype: "fields" and rowsource: customer.name+contact+address+cust_no
3. click on combo box, dropdown shows customers, pick is fine.

The problem arises when i add ONE or more customers to the customer table.
1. open form "Invoice Entry", click on combo box, immediately i get the dreaded error: C0000005 and application crashes.

when i delete the customer entries over 100 app works fine no problem.

Is there a limitation to the entries allowed in a combo box? they are running on an old PC with Win98.
I have duplicated the error on my laptop which is running XP sp2.

Any ideas would be appreciated.

terry