AutoCADLT Won't Launch

Issue: After installing AutoCAD you click the icon and get nothing.

Try this:
Control Panel
System
Advanced Tab
Performance Settings
Data Execution Prevention click on "Turn on DEP for all programs and services except those I select:" Add acadlt.exe to the list, check the box and restart your computer.
Click on the icon....

FlexLM Timeout on Slow Network

I'm starting to think that this blog should be called FlexLM in Plain English...I don't usually just cut and paste but this time I will. Another reason why you might not be getting a license...

Autodesk Support Number: TS1057817

Issue

When you tried to obtain a license remotely for a network-licensed AutoCAD® 2007-based product from the license server, you could not. However, you were able to obtain a license for a previous version of the product.
You were first presented with the FLEXlm License Finder dialog box, and then you received the following error message:
A valid license could not be obtained by the network license manager.
Error [1.5.-15]

With some products, you may also receive the following error message:
A valid license could not be obtained by the network license manager.
Error [1.5.-18]

Solution

This situation can occur when you access the license manager through a VPN, dial-up or a slow DSL/ISDN link.
AutoCAD® 2007-based products contain licensing enhancements that increase network bandwidth and latency requirements. To resolve this problem, it is strongly recommended that you increase network bandwidth or reduce latency to an acceptable level so the license management technology can function correctly.
If increasing network bandwidth is not an option, you can increase the amount of time the program waits for a response from the license manager by configuring an environment variable at the client workstation. Follow these steps:

1. Right-click My Computer. Click Properties.
2. In the System Properties dialog box, click the Advanced tab.
3. On the Advanced tab, click Environment Variables.
4. In the Environment Variables dialog box, under System Variables, click New.
5. In the New User Variable dialog box, enter FLEXLM_TIMEOUT for the name and 1000000 for the value.
6. Click OK to close each dialog box.
7. Launch the Autodesk application.

If you are able to obtain a license, the value of 1000000 microseconds (1 second) is sufficient. If you still cannot obtain a license, repeat the procedure; increasing the value in 1000000 microsecond increments until you are able to obtain a license from the license server.