1.) Create a fresh backup of your data. If you cannot sync to your personal computer then backup to an SD card. I'm not sure whether the older X5 included it or not, but look for a Dell utility on your PDA or installation CD called "Data Backup," which gives you the option of backing up all of your PIM data to a single file either using internal memory or, preferably, a storage card.
2.) Try performing a soft reset on the device. This usually works out any kinks without wiping out your files or programs. To quote Pocket PC Central, "The Dell X5 can be soft reset by pressing the recessed button on the left side of the unit. Under the left rubberized grip, there is a small dimple with the word "Reset" above it. Use the stylus tip to press this button through the grip. The device will perform a soft reset."
Hope this helps,
I have an Axim X5 that will not bring up the Contacts using any interface (i.e. the button, or from the drop down menu or home menu). When I try creating ''new'', it will let me create new Excel, Word, Notes, etc. but not even a new Contact- just a brief flash of the screen and it remains where I was.
I've done some occasional backup to an SD card including a backup today just before I discover this issue.
I'm not currently sync'ed to a PC since IT has not yet approved this device.