VB6+Access(ADO/JET) Randomly getting "Disk or Network Error" or "Cannot find the input table or query X on Database Y" -

we have practice management system 15 years old. i've been working on 12, , i've never encountered problem until recently, , can't figure out.

it written in vb6 uses ado/jet access access .mdb file on network. application opens connection when starts, keeps open while it's open, , closes when exits. lot of stuff db - system deals patient accounts, charges, payments, scheduling appointments, , million other things. have dozens of clients use program, each own db , of them 'offsite', have own server, number of workstations, between 1 , 20 users, pounding away @ system 24 hours day, 7 days week, , except occasional db field bug or having compact/repair dbs, it's pretty stable.

about 3 weeks ago, started seeing problem hadn't seen before. have 'in-house' system setup use: db on our server houses maybe 10 other dbs, , couple of people connect in system. started noticing if logged system, went straight our scheduler screen, , sat idle 5-10 minutes, might "disk or network error", or "cannot find input table or query x on database y".

what's strange seems happen when 2 or more people logged db different computers, , 1 of them error (randomly?) other 2 users fine.

there timer on 'main' mdi parent form of system wakes ever minute (there things change interval shorter interval, , there things disable timer, don't think either of them happening in situation). performs pretty basic sql query on db: select loggedin users userid = 'dbupdater' sql query seems triggering 1 of errors.

there timer runs every 2 minutes while user logged in check emails , few other things running during time. , since on scheduler screen, there's timer on there runs every 30s or check db see if changes scheduler have been made see if needs refresh screen or not.

there other strange things: db , users table seem fine. when person gets error logged system - 5 minutes earlier - system had @ users table mark them logged in, , i'm 100% sure query it's dying on had been run @ least once - 4-5 times before dies.

once user gets error, if leave error's messagebox on screen (not quit .exe), if try access db file in way, "disk or network error" - includes if try open db in access. however, can still network fine, , open other mdb files in same folder 1 can't open. other people on other computers can open mdb without errors. once user acknowledges error, , allow exe close, can open db file again fine.

i'm told not in anyway network issue. our guy says he's run pings , traces , sorts of tests ensure network connection not getting dropped. i've run things on db make sure it's not corrupted , seems fine - , happen on other dbs.

if has seen , knows possible fix, appreciate it! thanks!

new information (9/5/13 - 10:30am)

we noticed @ same time error, in errorlog on computer gets error warning event says:

{delayed write failed} windows unable save data file \medtechserver\medtech data\vb\schedtest2\medtech.mdb; data has been lost. error returned server on file exists. please try save file elsewhere.