I just purchased an Optimus S at Best Buy on saturday and I had the same problem. The salesperson sucessfully downloaded one ID pack for me at the store and otherwise the phone is fine, but I couldn't install any ID packs after I got home and started playing with the phone. I was getting the same error saying that the download failed. The ID pack would start by all indications, but the download bar stayed at 0% and never moved.
By coincidence, I found the problem. I upgraded from a Blackberry Tour and I had contemplated taking my 2Gb memory card from my Blackberry and swap it with the one in the LG. I decided not to go that route and I used a card reader to transfer my photos and music from the Blackberry card over to my external hard drive.
I then plugged the LG into my PC with the supplied USB cable and set it to USB transfer mode. I then copied the music and photos I saved on my hard drive over to a FOLDER called DSCM on the internal LG card. Once transfered I unplugged the LG USB cable and navigated to the GALLERY folder and there were the photos that I transferred. I also checked the MUSIC app on the phone and my music was also there.
OK, to make a long story shorter, I could not understand why my ID pack downloads would always fail and not complete. I found out by coincidence
Well I noticed a sale on a 8Gb micro SD card and I decided I would buy it to give me more storage than the included 2Gb that came with the phone.
When I removed the 2Gb card from the phone and inserted the 8Gb card, that was straight from the new package and tried to go to download an ID pack. VOILA, IT DOWLOADED!!! I could now download and install any ID pack that I wanted.
I think that the problem is caused when you take the old memory card from a previous phone and insert it in the Optimus with odd folders and directories that the phone can't read or when you COPY files onto the included 2Gb card already in the phone and you put them in the DSCM folder, which is what I did by mistake.
If any of you have this problem, try using a clean formated micro card in the phone and see what it does. I realize that some of us have photos and music from our old phone that we want to transfer to our new Optimus S. Tip here is that you can do that, but it has to be copied straight over to the card in the Optimus S when in USB mode.
Do not transfer ANY of your old music or photos into ANY directory that shows up on the phones memory card. I wouldn't recommend creating folders on the micro SD card inserted in the phone either. Looks like the phone already sorts out what is music, video and photos.
If you have this problem, try a clean formatted micro SD card in the phone and see if your ID pack downloads now work.
Sorry for stretching out this explanation. Hope this helps.