From your post I'm assuming that this database has not been split into a Front End/Back End configuration.
Having multi‑users sharing a single, non‑split database, sitting on a network drive is the sure way to repeated episodes of corruption. Multi‑users simply have to work off of a split database, with each user having their own copy of the Front End, with everything except the data/tables, on their respective hard drives, and a Back End with the tables/data on a shared drive.
Being in forced retirement, I spend 6-8 hours a day here and on other Access forums/newsgroups, and over the past six years have seen dozens and dozens of reports similar to yours! The really insidious thing is that they can work for extended periods before going bad. But once it does, the corruption becomes chronic, which is to say it occurs over and over and over again!
The record, by the way, was a non-split db that had been working, without problems, for 14 years! It then started exhibiting the exact same symptom you describe here.
In this scenario you simply have to bite the bullet and split your database.
Linq ;0)>