[GT540 Optimus General] effortless.:
All I can suggest then is installing a custom kernel or ROM I'm afraid.

Here is how you can.

Download this:

http://www.mediafire.com/?imautlh0m29cl2t

This has a fastboot ROM that enables fastboot + recovery so we can flash custom roms.

How to install (Guide from MrMentality @ MoDaCo):

1. Go to the Market and install 'MyBackup Root', open it and do a backup of your apps and personal data (contacts, sms, call log etc.) Once this is done, go to Settings>SD Card and Phone Storage>Unmount SD Card, a notification in the notification bar should appear saying 'SD Card safe to remove'. Remove the battery cover and remove the SD card and store it in a safe place. Then continue to step 2.

2. Extract the .zip file you downloaded to your computer (e.g. your desktop). Open the folder and install MSXML 4.0 SP3 Parser (msxml.msi).

3. If you have your Drivers installed, then skip this: Once that has finished, install LGAndroidDriver_WHQL_ML_Ver1.0_All_Win7.exe which are the drivers so your computer will recognize your phone.

4. Next, open KDZ_FW_UPD.exe

(i) Change 'Type' to '3GQCT' *THIS IS A MUST, THE UPDATE WILL NOT WORK OTHERWISE AND YOU MAY BRICK YOUR PHONE*

(ii) Make sure 'PhoneMode' is set to 'DIAG'

(iii) Browse for the 'V20B_00+Fastboot.kdz' file.

5. Prepare the phone by enabling USB Debugging by going to Settings>Applications>Development>Enable USB Debugging and connect the phone to the computer via USB cable and wait for the drivers to install for the phone.

6. Click 'Launch software update' and do not use your computer until the update is complete. The update will take roughly 10-20 mins to complete. When phone has rebooted, re-root your phone.

Installing recovery:

You have multiple choices to choose from.

ClockworkMod Recovery 2.5.1.8 (Recommended)

ClockworkMod Recovery 4.x (Recommended but you may run into incompatible .zip files, download the recovery_clockwork_x.x.x.x_swift.zip file)

Amon RA 2.2.1 (Recommended but has issues with recovery backups and usb toggle)

Amon RA 1.7.0.1 (Not recommended due to incompatibility with zip files and recovery backups. Also .zips must be signed)

Download the recovery image of your choice (I recommend 2.5.1.8)

Next put your phone in Fastboot mode by rebooting then holding Camera+Power, make sure USB Cable is plugged in. Also let Windows search Windows Update for drivers.

Download fastboot.exe from here: http://adf.ly/2M8Hi and extract it to the desktop. Also put the recovery image you downloaded onto the desktop too.

Open a command prompt and type the following:

cd Desktop
fastboot devices (if you see ? fastboot then your device is recognized)
fastboot flash recovery name_of_recovery.img
fastboot reboot

When fastboot says rebooting, hold down HOME and wait. You should see clockwork pop up. And there you are, recovery on your phone!

Now to install a custom kernel/rom. If you are happy with Android 2.1 and want tethering, go to step 1 and skip step 2. If you want the bleeding edge and want the latest and greatest Android version, skip step 1 and go to step 2.

Step 1:

Download the boot_666_MMXTREM_init.d.zip from here. Also grab addons.zip from here.

By using the volume keys, go down to Mounts and Storage, press call button, then go to Mount USB Storage, press call button again. On your computer, put both .zip files on the SD Card. Then press call button on phone. Press back until you are at the main screen. Now go to 'install .zip from sdcard' press call to select and press choose .zip, then go down to 'boot_666_mmxtrem.init.d.zip' and select that, then go down to yes and then select, wait until install finishes. Now go back into install.zip and do the same for the addons.zip. When that is finished, go back to main screen and go to 'advanced' and select Wipe Dalvik cache, select yes, wait and then reboot phone. Now try to tether and it should work no problems.

Step 2.

Download any ROM you want from the GT540 section here on XDA.

It will come in either three formats.

Fastboot- boot.img and system.img

Recovery .zip- a .zip file that contains boot.img, and two folders, META-INF and system. DO NOT EXTRACT THIS.

Recovery Backup- boot.img, system.img, data.img, and nandroid.md5

For Fastboot, put phone in fastboot mode, put system.img and boot.img on the desktop, open a command prompt and type:

fastboot -w
fastboot erase system
fastboot erase boot
fastboot flash boot boot.img
fastboot flash system system.img
fastboot reboot

For recovery.zip, put the .zip file on SD Card (if you are downloading SwiftDroid Recovery version, extract the SwiftDroid_x.x.x.x_recovery.zip put the update-cm-xxxxxx.zip file on your SDCard, not the SwiftDroid.zip one. Then flash in recovery like described in step 1. Remember to factory reset to avoid bootloops.

For recovery backup, put the folder in the ClockworkMod\backup\ folder on the sdcard. Then go to Backup and Restore, choose restore and then choose the backup folder.

Hope it resolves your issues! :D