[AccessD] Back-End DB is locking...WHY?!

I just inherited a program from someone else...a non-programmer, who used some of MY original code and thought she was a programmer...very sore subject...especially today.
 
Anyhow, she had three people sharing a single Access DB (.accdb) on a common network drive. Somehow it was working for them...until it wasn't. The did some cleaning up of their file structure the other day, and they renamed some directories, and it no longer worked. 
 
I told them that I was surprised it was working in the first place, and that I wouldn't spend time figuring out "why" but I'd fix it the right way. To make a long story short, I got all the tables into a single DB and then used database splitter to create a front-end/back-end situation. 
 
This is the first time however, that I am seeing a back-end gain a lock file (.laccdb).  I split the DB, yet it is still a single-user program...and I have no idea why.
 
I suspect...but I'm trying to keep an open mind...it has something to do with the fact that it was a "front-end" program of my original that she used at the beginning...her beginning anyhow. 
 
Does anyone have any idea what I can look at to prevent...stop...this from happening? Please help someone who is having a very bad day...
 
Thanks in advance!
 
John W Clark
Computer Programmer
Niagara County

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