How do I get the pmln5993 set to pairing mode?

I had the same issue, fixed by using the Manual mode for pairing. From the manual:

2) Manual Pairing (Pairing with another phone or re-pairing)
a) With the Power off, press the CALL button and move the power switch to the
'ON' position at the same time for 4 seconds.
b) When the headset enters Pairing Mode, the LED indicator will show a solid
blue light. After the procedure repeat Easy Pairing steps c through f.

Steps C through F are to go to the bluetooth settings area and manually select the HBS-700 for pairing.

forget the headset
turn bluetooth off
turn the headset device off
reboot phone.
try again

Turn on the Bluetooth on your phone first and then long press the button on the headset until you see the alternate blue-red light repeating and release the button quickly. Your phone will discover the headphone now withe name "ZBT1099" pair with it and If asked for the pass key in phone give "0000". You are all set!! :)

Make sure you are in "pairing mode" by holding down the Multi Function Button (MFB) until the red and blue flashing alternately. When the device is off, holding down the MFB for about 5 secs will turn the device on; however, don't release the button and continue to hold until red and blue flashes. Then, you are in pairing mode.

In order to pair a BlackBerry device with a Bluetooth device, the Bluetooth device must be in pairing mode. Most Bluetooth devices are not set to pairing mode by default. Therefore, refer to your Bluetooth device manual for instructions on how to set the device to pairing mode.

1. On the BlackBerry device, in the device options, click Bluetooth.
2. Click the trackwheel and click Add Device. The Select Device list appears and lists devices that are in range and available to be paired.
Note: Only devices that are in range and are in pairing mode will appear in the available device list.
3. Click the device to which you are pairing. The Enter passkey dialog appears.
4. Enter the passkey to authenticate the device. Most Bluetooth devices contain a hardcoded passkey. See your Bluetooth device manual for the passkey.

Best regards

In order to pair a BlackBerry device with a Bluetooth device, the Bluetooth device must be in pairing mode. Most Bluetooth devices are not set to pairing mode by default. Therefore, refer to your Bluetooth device manual for instructions on how to set the device to pairing mode.

Be sure the the headset in in 'Pairing' mode.
When in pairing mode, the light should be flashing red and blue or have a steady blue.
The put most headsets in pairing mode, turn headset OFF, then hold the power button until it goes into pairing mode as discribed above.
Then you can discover it with your phone or PC. Pin (pass key) should be 0000 (4 Zeros) or try 1111, 1234, 9999

In order to pair a BlackBerry smartphone with a Bluetooth enabled device (e.g. a Bluetooth enabled headset), the Bluetooth enabled device must be in pairing mode. Most Bluetooth enabled devices are not set to pairing mode by default. Refer to your Bluetooth enabled device manual for instructions on how to set the Bluetooth enabled device to pairing mode.
To pair the BlackBerry smartphone with a Bluetooth enabled device, complete the following steps:
1) On the BlackBerry smartphone, click Options > Bluetooth. If you cannot find the Bluetooth option,
2) Open the menu and select Add Device. The Select Device list appears and lists Bluetooth enabled devices that are in range and available to be paired.
Note: Only BlackBerry smartphones enabled with Bluetooth technology that are in range and in pairing mode will appear in the available Select Device list.
3) Select the Bluetooth enabled device with which you are pairing. The Enter passkey dialog appears.
4) Type the passkey to authenticate the Bluetooth enabled device. Most Bluetooth enabled devices contain a hard coded passkey. See your Bluetooth enabled device manual for the passkey.
Note: 0000 is the universal passkey for pairing any Bluetooth enabled device with a BlackBerry smartphone.
Note: Once a Bluetooth enabled device is paired, it appears in the Paired Devices list. The Bluetooth enabled device will no longer appear in the Select Device list.
Bluetooth devices are manufacturer specific. Please refer user manual for instructions on how to pair with other devices.

This worked great for me... I got the headset in "pairing" mode by following these instructions. Then set my BB Curve 8350i to "discover" bluetooth devices. It discovered the headset and asked for a PIN number... one of the other articles I read said the pin was "0000" so I put that in and - PRESTO - it works

Make sure the Jabra headset is set to pairing mode, otherwise the phone cannot find the headset. The manual should have instructions to set the headset in pairing mode. While the headset is in pairing mode, have the G1 search for the headset (Settings > Wireless Controls > Bluetooth Settings). When it finds the headset select it and type 0000 for the PIN code.