Problem with Siemens TP 1500 Basic

Hi,
I have this problem with communication between Siemens TP 1500 Basic and VIPA PLC (CPU 315SN). There is connection between these two devices but some times there is system error message on the panel, which say that there is an error in some tag(most of the times bit tag) - "PLC address error". But when I press the buttons that set/reset this tag its work.

Any ideas?
Thanks

Now, I tried with Siemens CPU 315-2 PN/DP but there is no difference!
Please help!

One last try.
If somebody have an idea please tell me.
I have written to siemens forum too but no body answers me.

For the project with the 315-2PN/DP, try to make it an integrated project. And let the CPU connection be fully defined by selecting the 315-2PN/DP CPU in the connection dialog in Flexible.
Then make a "rebuild all".
Check the "output window" to see if there are warnings. Most warnings are not so severe, even if tags are wrong, so the project will compile and run - even with minor errors.

See how that goes.