There is a fix, and no it is not deleting all your apps to get it to go away.
Basically for some real dumb reason HTC has given the data/data folder 150MB of storage space and when that gets close to full you will not be able to add anymore apps to your phone. So even if you have 5+GB of space left you are stuck.
But there is an app in the market that I was a little leary on trying at first but after getting it and seeing that it works great I wanted to share this with everyone.
This is the app:
NotEnoughSpace | AppBrain Android Market
I was able to move Google Earth's 16MB to the partition this app created and have it work, and freed up all that space in my data/data folder.
BTW INSTRUCTIONS FOR USE:
1) Create a partition (I made a 1GB one on the phone in emmc)
2) Pick an app taking up a lot of space (like Google Earth) the app will show you how much space each app takes up in the data/data folder so you will learn why you are having an issue.
3) Click to open up the app (Inside NotEnoughSpace of course) and click all the sub directories (most apps have 4-5) and move them ALL to the partition.
That's it. And you can always move everything back if you want. But just note that if you move the app itself OR don't move every sub directory the app wont work after a reboot. Took me a few tries and multiple reboots to figure this all out but now I am good to go and freed up much space.