Auto expand .. in a combo box

[MyQuestion]

Hello,
I am facing problems with the auto expand function in combo boxes. The whole database program is running for many years. Some weeks ago the "fill in as you type" didn't work. I checked the "auto expand" settings in all three combo boxes of that form, but they were on. I replaced the form from a back up file. Than it works, but after restarting the database, the problem remained. I tried to test it on an other computer, without success.
Can someone help me??
Thanks in advance!
Ulf

[June7]

Did you search web?

Bing: combobox autoexpand not working

There are a lot of hits indicating variety of possible causes, including corruption of the combobox resulting from a query edit.

I've never had this issue.