Resized partition problem.

You should change bootloader configuration after that because if you deleted some partition you changed partition table. For example:
You have one disk hd0
Partition table looks like:

/dev/hda1 win xp
/dev/hda3 vista
/dev/hda5 linux

After change you have

/dev/hda1 vista
/dev/hda3 linux

How exactly would you do so?

First, you have to know disk name. Just run df -k under ubuntu, then run cfdisk /dev/xxxx where xxxx is name of your disk. In this tool there is list of your partition, note name of partition with FS type <> Linux ext3 or raiserfs, and list this partition in post.
If you are using lilo you have to change partioion name in /etc/lilo.conf, if you are using grub the best way for you is use wizard, grubconfig or something like that, I don't use grub, but if you type grub and push TAB key you get possible commands.

Thank you for the information.