We usually see a pattern.  There are a few "very common" problems:

(1)  LOCAL SHARE is not TRUE in the BDE Configuration.  Especially a problem
if you're using the database on what is, to you, a "local" drive that is
also shared with others.

(2)  NET FILE DIR setting is missing or incorrect.  [Always check that locks
do in fact get placed, and are in fact respected, when adding a new
workstation.]

(3)  Un-diagnosed network cabling or card problem.

(4)  Trying to connect to a database over a wireless LAN.

(5)  Disk error; ScanDisk says "found errors on this drive and fixed them
all."  Appearance of any FILEnnnn.CHK files in "C:\".

(6)  Using an unlimited or excessive "time out" value on locks and so-forth.  
Users give up and do a three-finger salute on their machines.

It's very important also to be =preventive= in your maintenance of the
system.  =Look= for problems, before they are recognized.

Be sure to run /recent/ and /consistent/ versions of BDE.  If a problem
arises -- "opportunistic locking" and "cacheing" have been mentioned -- and
that problem has been fixed or addressed, you're going to need to be
running the current stuff in order to find it.

See:
        http://www.borland.com/devsupport/bde

Releases of BDE are generally version-compatible.