Question: Sometimes I download an app but it fails to download or install. The message just says that, no further details. It generally seems that the app never installs after that. Is there anyway I can find out more details about why it failed? Is there any good way to get stuff to install after this has happened.

I am using Android 1.5 on a T-Mobile Pulse/Huawei U8220

Answer: 
When this happens to me there's one thing that helps every time:

Open the Market and go to the Downloads section, then perform a long click on the stalled download. Cancel the download from here. Now you should be able to reinstall / update the app.
Are you out of internal storage for apps? Have you tried a hard reset? Can you upgrade your phone to a newer Android release? Personally I would try upgrading your device first then see if you still have problems.