C++ runtime errors with Oracle forms

I am geeting an intermittent errors with Oracle Forms (runtime) version 6.0.5.33.0 DB version 8.0.6.0.0 when I am carrying out operations on two open forms.

When, for example a form is used to submit an application report request and then minimised so that I can enter data in another form (already open underneath) the following error sometimes occurs :

Firstly a Mircrosoft Visual C++ Runtime Library popup window appears stating that

"Assertion failed! in Program: E:\orant\BIN\ifun60.EXE
File: E:\f992w32\if\iff\ifrlf.c
Line: 890.

Expression: 0 "

Next an Oracle Forms 6.0 popup appears stating
"ERROR: Failed to open file: ifrun60_dump_201"

(though I think the number at the end of this message increments with each successive crash).

Finally the front end crashes.

The same kind of errors occur intermittently when cutting and pasting date fields between 2 forms

The operating system is WinNT4 SP6

I am relatively new to Oracle Forms. Has anyone seen anything similar to this and can any Oracle gurus shed any light on this ?

Thanks.