I put a AT&T sim card in A sidekick lx and it freezes after a while and loads up long what is the problem the sim or the phone

You can unlock the Sidekick LX from Jamica Network digicel using the Unlock code ,you can get the Unlock code within 0 to 5 Hours(approx) you can get the code at reasonable cost here Simpleunlocking.com and Unlock it ,then you can use it with any GSM Network Sim card....Follow the instructions below and Unlock it step by step...

Sidekick LX Unlocking InstructionsWarning : Do not enter any wrong unlock codes on your Sidekick LX mobile phones. If you enter over a certain amount of wrong unlock codes on your Sidekick LX mobile phone, your phone may get hard locked and sometimes become unusable.
1. Switch ON your Sidekick LX with a Not ACCEPTED SIM Card.
2. If your Sidekick LX asks for a PIN code, then enter your SIM card PIN and press OK.
3. Sidekick LX will ask to enter an "unlock code".
4. Enter Unlock Code we send to you.
5. Your Sidekick LX is now unlocked.

*NOT ACCEPTED : We mean, to use a Sim card from a network other than the network your Sidekick LX is locked to.

More than likely your contacts are still located in the old phone. Replace the Sim card back into the old phone and copy the contacts onto the Sim card, place back in your Sidekick and you then can locate your contacts.

It says just Network lock only,You need to enter the Code if it locked Network mean.You can get the Unlock code at here
http://www.superunlockcodes.com/sidekick-lx-2009/rs12wp9/ and Unlock it,get the Unlocking Instructions below to unlock it step by step.
Sidekick LX 2009 Unlocking InstructionsWarning : Do not enter any wrong unlock codes on your Sidekick LX 2009 mobile phones. If you enter over a certain amount of wrong unlock codes on your Sidekick LX 2009 mobile phone, your phone may get hard locked and sometimes become unusable.
1. Switch ON your Sidekick LX 2009 with a Not ACCEPTED SIM Card.
2. If your Sidekick LX 2009 asks for a PIN code, then enter your SIM card PIN and press OK.
3. Sidekick LX 2009 will ask to enter an "unlock code".
4. Enter Unlock Code we send to you.
5. Your Sidekick LX 2009 is now unlocked.

*NOT ACCEPTED : We mean, to use a Sim card from a network other than the network your Sidekick LX 2009 is locked to.
Each Sidekick LX 2009 mobile phone has an unique unlock code. You can buy the unique unlock code for your Sidekick LX 2009 mobile phone using the form above.

i put my sim card into my phone and it says enter special sim code

if you are using the same carrier you can, just change the sim card to the sidekick and you should be fine.

I just got a sidekick off the internet and I put my SIM card in the phone and it says no SIM card. What do I do? Anyway to fix whatever is wrong?

under the battery slide it in

just ask the phone company provider for your PUK2 AND PUK codes.
when you get them go to the jump menu dial
**05*PUK*passcode*passcode#
the passcode is any 4-8 digits you'd like, that are NOT, AND I REPEAT N - O - T consecutive.
(for example 2736 is good whereas 1234 or 9876 is bad)
if it asks your for the code again put in the PUK2 then go to settings> network options goto the "scan and select manually" button and chose your carrier.

You might have to get a new phone and sim card... 

works for sk 3, slide and lx.
the video says only at&t in the U.S. but... i've seen it work for fones in europe.
try it.