Mint,Ubuntu,Win 7 triple boot problems!

[Aub_Pro]

Problem #1- Ok so i had win. 7 and Mint 14 dual boot working fine, mint was installed fully on 32gb usb flash drive and windows 7 on my internal hard drive. I decided to try and install ubuntu on my external hdd to have a triple boot system in theory...wiped usb flash drive and put ubuntu on it to install it fully on 50gb partition on external hdd "Error:no such partition grub rescue" after install on boot (forced usb boot in bios).

Problem # 2 - Then i figured that was a failed attempt i will just go back to my dual boot that worked before, wiped usb flash drive and put mint 14 dvd in drive and tried to fully install it to my 32gb usb flash drive. In the mint installer when i try and delete the 32gb flash drive so i can partition it how i want for proper install it gives me a crash error "ubi-partman failed with exit code:141" ????? Reboot back into windows 7 and attempt to remove my mint dvd from dvd drive....dvd drive will not open so i attempt to uninstall dvd rom drivers and restart, doesn't get it working again. I must first boot back into mint from the usb flash drive and then back into win.7 and bam dvd rom works????
What the heck is going on with my system lol help would be appreciated in understanding what is going on.

~Linux Newb ~

[Aub_Pro]

*Update*
Fixed MBR with windows 7 disc didn't seem to change anything.
Formatted flash drive with bootice and was able to install linux fully onto it, linux installer or gparted wouldn't format it for some reason. Currently have dual boot win. 7 and ubuntu but like the subject says i would like to have a tripe boot system by installing mint on external hdd, is it possible?

[pfeiffep]

I have successfully installed Linux Mint onto a USB external hard drive which I found faster than installing the entire OS onto a flash drive.
I also have a tripple boot HP tower, however the 'second' drive is internal