Just exclude the truecrypt directory from scanning and wait until a fix from avast is available. You don't need to disable avast entirely.
You need to use the Exclusion lists:
For the
Standard Shield provider (on-access scanning):
Left click the 'a' blue icon, click on the provider icon at left and then Customize.
Go to Advanced tab and click on Add button...
For the other providers (
on-demand scanning such as the screen-saver or the Simple User Interface):
Right click the 'a' blue icon, click Program Settings.
Go to Exclusions tab and click on Add button...
You can use wildcards like * and ?.
But be careful, you should 'exclude' that many files that let your system in danger.
