I am programming ATMEL 89C51RC2 with ISP using Flip-SW.

I have programmed about 50 pieces and following troubles occured:

*) Sometimes I get a 'time-out' error; Flip can not connect. IO pins of the uP does inpredictable switchings. Sometimes, new power up solves this problem, but in some cases, uP seems to be dead.

*) Programming was successfull, software on 89C51 is running perfectly, even if I switch on/off power for many times. If I leave power switched off longer (over night), next power-on fails (in first case, uP does nothing, in second case, uP starts up again and again in about 1s interval). In this case, a re-program with the same software solves this program.

Do someone have similar problems or can someone tell me, how to solve this problems (is it my hardware, uP-software or the way I do programming the flash)?

Thank you in advance!