SharePoint login page doesn't seem to load styles from /_layouts, throws error "value cannot be null"

Answer 1

The issue appears to be the fact that a web.config in the layouts directory has batch compilation set to false.

I had the same issue. The web.config in C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\LAYOUTS contained this line:

<compilation batch="false" batchTimeout="600" maxBatchSize="10000" maxBatchGeneratedFileSize="10000" />

The line should read:

<compilation batch="true" batchTimeout="600" maxBatchSize="10000" maxBatchGeneratedFileSize="10000" />

For more information: Fixing the Elusive “Value Cannot Be Null” FBA Authentication Error

UPDATE 11/30/2009: FYI. It appears that this doesn't actually fix the issue, but it appears to expand the time between errors.