Please help me adb mount RW

Hy !
My name is Chris,from Romania.
First,excuse me for me poor english !
I have a Prestigio PMP5100 tablet. I replace original firmware with Arnova 10 rooted firmware. It work fine,but the partition not mounted R/W and I don`t have access system files.I install USB drivers,JRE,JDK,Addroid SDK.
With "adb devices" my tablet apear connected.
With "adb shell" I tasted :
su
mount -o remount,rw -t yaffs2 /dev/block/mtdblock3 /system

apear :

#su
su
#mount -o remount,rw -t yaffs2 /dev/block/mtdblock3 /system
mount -o remount,rw -t yaffs2 /dev/block/mtdblock3 /system

My problem is how to continue ???
If press ENTER key apear new line with # :
#

Please help me.
Thank you in advance,and have a nice day.