try updating your software to 1.93 rom, i was having the same issues when i was on 1.37 and my partner was on 1.35 updated and not had the issue since!
update site - http://www.htc.com/www/supportdownload.aspx?p_id=133&cat=2&dl_id=2
also if that doesnt work try doing a soft and/or hard reset -
Performing a soft reset
Perform a soft (normal) reset to clear all active program memory and
shut down all active programs. This is useful when your device is
running slower than normal, or a program is not performing properly. If
a soft reset is performed when programs are running, unsaved work is
lost.
To perform a soft reset
1. Pull out the stylus, then remove the back cover.
2. Use the stylus tip to press the RESET button (red) located at the
opening of the stylus bay. Your device restarts and displays the Home
screen.
HTC Touch Diamond 2 hard reset
Performing a hard reset
If a normal reset does not solve a
system problem, you can perform a hard (full) reset. After a hard
reset, the device is restored to its default settings-the way it was
when you first purchased it and turned it on. You will lose any
programs you installed, data you entered, and settings you customized
on your device, and only Windows Mobile® software and other
pre-installed programs will remain.
Warning! Your device will be
set back to factory default settings. Make sure that any additional
installed programs and/or user data have been backed up before you
perform a hard reset.
Important If Encrypt files when placed on a
storage card is enabled, backup all files from the storage card before
using Clear Storage, hard reset, or updating the operating system.
Otherwise you will no longer be able to access the encrypted files on
the storage card. Use ActiveSync or Windows Mobile Device Center to
transfer files between your storage card and computer. After the
procedure, copy your files back to the storage card.
To perform a Diamond 2 hard reset
1. With the
device
turned off,
press
and
hold
the
VOLUME UP and VOLUME
DOWN buttons,
then
briefly press the POWER button.
2.
Continue pressing
the
VOLUME UP
and
VOLUME DOWN
buttons
until
you see this
message
on the screen:
3.
Release the
VOLUME UP and
VOLUME DOWN buttons.
4.
Press
the
VOLUME UP
button to perform the hard reset, or press any other button to cancel
the reset.
