The "Analysis options" tab lets you configure how tokens are handled, and which types of tests are performed during the analysis.
These settings control how tokens are handled during analysis. The following options are available:
These options control the types of analyses that are performed. You can individually enable or disable each type of character-level and bit-level test. Sometimes, after performing an initial analysis with all tests enabled, you may want to disable certain tests to reflect your better understanding of the tokens' characteristics, or to isolate the effects of any unusual characteristics manifested by your sample.
In the results window, after modifying any of the analysis options you can click the "Redo analysis" button to re-perform the analysis with your new settings, and update the results.
Get help from other users, at the Burp Suite User Forum:
This release fixes a bug which was introduced in the v1.5rc2 release, and which caused the active scan checks for XSS to fail to execute in some situations