Heidenhain TNC 355 transfer from PC problem.

Hi there,
I have several CNC machines but one give me a headache from few days ago. It was working fine but it seems to be a trouble to connect with PC now. The machine is Mikron WF62C with Heidenhain TNC 355, TNC server setup (for FE)right as books said, 7 data bit, 1 stop bit, even parity, X-on/off, machine parameters MP217 0P, MP218 17701, MP219 21285, MP220 279, MP221 5382, MP222 164P, MP223 0P, MP 224 4, MP225 0P...etc.

I was working (my workers) for almost two years without any trouble, and now it seems that something goes wrong. When I try to send any program (written in H code) from PC trough FE settings (settings that worked), machine gave me the error input output notice...(problem with DSR, bad cable etc..). This is when I connect trough 25 pin/9 pin cable from TNC to PC. But when I try to use the USB to RS232 9 pin it haves different notice, the program goes to upload but stops the TNC server after first row BLK FORM...and stays in that form!?

I was read several posts here and it sims that I have trouble with transmitter and receiver RS232, I checked the cable 25pin to 9 pin it seems to be fine (with multimeter)….It bothers me what happened to got in that issue. How to check is it really the transmitter receiver problem on board of TNC 355 (2 EUR issue IC RS232 parts on MOUSER electronic website) or it seems that something other goes wrong.

Anyone haves the same problem or knows what can be? Help?