data connection turns itself off?

[av8or]

i've been noticing that overnight now, my diamond turns its data connection off and i wake up to find the ballon saying it was unable to connect to the "network", even though the Ev icon is still up in the status bar

i go to the settings tab then communications and sure enough, the data switch is off, flick it back on and all is good

has anyone seen this before? tried searching but couldn't find anything specific to this issue

addendum:

ok just had it come up again, i've done soft resets and it doens't seem to affect it but here is the bubble

Cannot Connect
Dialed: #777
Cannot connect for an unknown reason. To
check your connection settings and change
them if needed, tap Settings. If the problem
continues, reset your mobile device
according to your manufacturer's
documentation and try again.

now i wasn't doing anything, phone was just sitting on sofa next to me charging since the one earlier