It is always helpful to include the version you are using, where is is installed (i.e OS installed and used for collecting...laptop? GPS and type, etc.), whether is is an out-of-the box or customized collection tool, and if you are using the ArcPad Toolbox in ArcGIS Desktop (version) and the type of data (i.e. SDE or maybe a personal GDB?).
I'm rather rusty on ArcPad (other than my custom apps), but those items should help others troubleshoot.