Comment 1 for bug 376269

Thanks for reporting this bug and any supporting documentation. Since this bug has enough information provided for a developer to begin work, I'm going to mark it as confirmed and let them handle it from here. Thanks for taking the time to make Xubuntu better!

Perhaps the following will assist you in getting a higher resolution in the meantime:
https://wiki.ubuntu.com/X/Troubleshooting/Resolution#Problem:%20%20Autodetection%20results%20in%20reduced%20resolutions%20available