Combobox pulling data from external source crashes randomly

[dhwreck]

I have an invoice spreadsheet that is used to create one months’ worth of invoices and tally all the invoices. The invoice spreadsheet has a master invoice which is duplicated to create 60 to 90 invoices each month. The master invoice has a searchable combobox which draws information from customer spreadsheet. Each invoice sheet (duplicate of the master) that is opened sends information back to the customer spreadsheet which allows the appropriate search to be conducted. This all works fine. The combobox works fine; however every once in a while the customer data file seems to lock up which causes the invoice spreadsheet to lock up only when the combobox is being used. The crashes are random. Sometimes you can search with the combobox with no problems then all of sudden it crashes.

I need a cold set of eyes to see if anyone can spot the issue. The two files have to be saved to the drive and directory D:\excel and both files need to be opened for this work. If someone can test the combobox of a new invoice sheets eventually it will cause the files to crash.

I appreciate any suggestions on preventing the two files from crashing.