Nick, if what tina said dosnt work then you may have to try this:
if your client crashed during the download, you may have to wipe the FTB folder in the users directory - it saves backups in the form of xml documents ... if the xml survived the download you will get an invalid pack error when attempting to load the modpack again.
C:\Users\[yourusernamehere]\AppData\Roaming\ftblauncher
Make sure that you can actually search for hidden objects, or your users folder wont show up.
As for texturepacks, i found that soartex while it dosnt have as many addons as sphax, does allow you to download and add texture items to the pack using its own executable, this means you download the .exe, run the program and you pick what textures you want for your installation, it will then download AND zip them for you ... all you have to do then is place them in the correct folder.