Unity Pro trial crashing due to an asset

I downloaded Unity 4.5.2 and activated the free trial of Unity Pro. When I downloaded my first asset I was given the option to import it or not. Being a novice, I assumed that if I didn’t import the asset I wouldn’t be able to actually use it in a project until I did. So I imported it and all the assets I downloaded after that. After a while I got an error message regarding one of the assets and Unity became unresponsive so I had to close it using task manager. I opened Unity again and it started to import an asset, then it gave me an error message and crashed. I uninstalled Unity including the registry leftovers using revouninstaller and reinstalled. It still didn’t work. It would open, start loading assets and then crash. I tried the AppData trick and that didn’t work either. What can I do?

Is there a way I can start fresh with a clean version of Unity (nothing installed) and download the products I want again?

-Tomboy

This happens because data for the asset in the project’s Library folder got corrupted during the failed import. Unity then attempts to reimport it but comes across some bad data in Library, and crashes.

You can often fix this type of error by removing the offending assets from the project. When the file is no longer there, Unity won’t try to import it upon opening, and thus won’t crash. You can then add the asset again after the editor has successfully opened, and it will usually work, but the editor has to be fully open when you re-add the asset manually.

In the future, you can protect yourself against such crashes by turning on *.meta files. Meta files are a mechanic Unity developed to enable the use of versioning software such as Tortoise SVN in teams of developers. The meta files contain the same information as the local Library folder does, but spread out alongside the files. If the Library gets corrupted in the future again so Unity won’t open, you can simply delete the whole Library folder and have Unity restore it when opening. Everything will still be as you left it as the data is recoverably from the meta-files.

Without the meta-files, however, you need to identify the offending assets yourself and manually remove them one by one temporarily until the editor opens again.

Bonus: If saving the project itself is of no importance to you and you simply just want the editor to open again, you can press and hold Alt while starting Unity. It will cause it to open a project dialog where you can select another project or start a new one, instead of having the editor constantly crash on opening the broken project.