Intermittant Error

A client reports that various users, doing various things, get the following error once in a while:

The following C/AL functions can be used only to a limited degree during write transactions (because one or more table will be locked).

Form.RunModal is not allow in write transactions.

CodeUnit.Run() is allow in write transactions only if the return value is not used. For example, 'OK:=CodeUnit.Run()' is not allow.

Report.RunModal is allow in write transactions only if ' RequestForm = FALSE'. For example, 'Report.RunModal(...,FALSE)' is allowed.

DataPort.RunModal is allow in write transactions only if ' RequestForm = FALSE'. For example, 'DataPort.RunModal(...,FALSE)' is allowed.

Use the commit function to save the changes before this call, or structured the code differently

This is NAV 5.0 SP1 on a Navision server (not SQL.)

The error occurs in odd places, like posting a PO (some modified code there), doing a bank rec (no mods there), etc. The users are alway's able to continue with hat there were doing with no (apparent) ill effects.

I've searched on this error and see references to it in NAV 4.0, and advise to click the 'Stop on first error' choice on planning reports. I searched all of the NAV 5.0 reports for this phrase and only found them in 99001017 and 99001020 - but these users are functions these users don't use.

Is anybody else running into this?