LP is probably a system app included in the UD 8.0 rom. for any system app included in any rom, you will not be able to automatically install an update from the mkt. but, if you "have to have" the update, there are several things you can try. (** i can't believe i don't have this as a cut and paste text - but i will now! **)
the easiest way is thru root explorer (unless UD has a menu option for deleting system apps). go into system/app, and then click the "mount r/w" button (to change the system files from read only to read/write). then find the LP app, long press on it, and then hit "delete". then push the "mount ro" button to change back to read only, exit out of root explorer and then reboot (this is important to get the change in system apps to "take.") when you boot back up, you should be able to install LP from the mkt, with the update, and then put in your code to unlock LP+.
the second avenue is thru Terminal Emulator. type in:
su
sysrw
rm /system/app/launcherpro.apk
sysro
reboot
again, it's necessary to actually type in "reboot" and enter, to get the change to take.
finally, you can go into the rom zip file, manually delete/remove the app, and then reflash the newly configured rom zip file w/o the system app. then you should be able to dl the updated app from the market.