Uart returning -1 when more than 1 uart opened in NIOS

hi,

I am using quartus 9.0.

and I need to use 5 uart cores in sopc (all 115200). when i am opening one uart in blocking mode in Nios, it reads/writes fine. bt wen i start opening other uarts, the same port starts returning -1 (only opening of other ports,no reading no writing).

I need to use all rs-232 ports..wat can be the problem?

sth like this

main()
{
uart1=open(uart1_name, mode)
uart2=(uart2_name, mode)



result=read(uart2, buffer, len) //gives error if uart1 is opened before uart2, alone it works fine.



}

I need to use all 5 rs-232 ports..wat can be the problem?:confused:
can we use only one uart core??:confused:

plz reply.