I have just now checked in both version 0.24 (likely the version used when the bug was reported) and version 0.29.

Seems to be fixed in version 0.29.

Decompiling of animations and their QC commands are unfinished features because no one knows how to decompile all of them correctly.

For L4D2 weapons, there should be known workarounds, which might include using files from the L4D2 Starter Kits.

The error message shown in the original post's image is (note that it is not intended to be a web link, but Steam makes it a link):
Error parsing
C:/Windows/Microsoft.NET/Framework/v2.0.50727/config/machine.co
nfig
Parser returned error 0xC00CE556

The error message seems to indicate there is a corrupt file in the .NET Framework files.

After a quick Google search, this looks like the best way to fix it:
Go to folder, "C:/Windows/Microsoft.NET/Framework/v2.0.50727/CONFIG/".
Make a backup copy of "machine.config" in case this does not fix the issue.
Copy "machine.config.default" file to a new file [machine.config (copy).default].
Rename the new file to "machine.config".

Reply in this topic after you try the above steps and let us know if they fixed the problem or not.

The problem is with Blender or Blender Source Tools, not Crowbar.

Fixed.

Portable binary:

• Crowbar_2015-08-03_0.29.7z[drive.google.com] (Released 03-Aug-2015) (189,935 bytes)

Source code:

• Crowbar_2015-08-03_0.29_source.7z[drive.google.com] (Released 03-Aug-2015) (297,120 bytes)

Changelog:

=== Decompile ===

• FIX: Reading a PHY file fails for models that previous versions of Crowbar read successfully.

Portable binary:

• Crowbar_2015-08-02_0.28.7z[drive.google.com] (Released 02-Aug-2015) (189,683 bytes)

Source code:

• Crowbar_2015-08-02_0.28_source.7z[drive.google.com] (Released 02-Aug-2015) (297,083 bytes)

Changelog:

=== Decompile ===

• FIX: If reading a PHY fails, the decompiling stops. Decompiling should skip the PHY file and continue.

=== Compile ===

• Added checkbox to Output Folder option to toggle between placing compiled files in game's models folder or in a custom folder.
  
• For "Use in View" button, set the View tab's Game value to the Compile tab's Game value.

=== View ===

• Insert a context menu into Info textbox that includes Copy and Paste items.

Well, that's unexpected. I've never had this issue, so not sure what else to tell you. Crowbar should run without any changes. Perhaps your Windows is set up differently.

Try watching this video on how to fix and choose the Crowbar.exe file instead of the one in the video:
https://www.youtube.com/watch?v=0OUdIZT7C2E

Upload a screenshot where you show the Crowbar.exe file and the Data folder.
Also upload a screenshot of whatever shows after double-clicking the Crowbar.exe file.