break connection on vpn establish

hello
i have a question about vpn, thanks for masters on answer it
my mikrotik has 2 active ether. 1 and 2 with ip address 192.168.1.1 and 192.168.2.1/24 . those not important
i configured mikrotik to connect vpn through ip pool , PPTP Server , profile and secret and at last doing nat for provide internet access to them.
those were all confige on my router.
there are true connection between lans
now my question is : when vpn is connected on a PC (it has internet access truly) , but connection of pcs on another lan to that PC will break (include of ping and other protocols).
how i can correct this problem (establish connection like first state)
thanks in advance.