Lately we run into problem that after applying PSA hotfix in this case (PSA_HF_2009SP1_046) after creating a new expense report the page was blank, but expense report was still created. It happen that mentioned hotfix modifies AOT \ Web \ Web Files \ Static Files \ Proxies.
The hotfix add following lines:

/class:PSAProjBudgetTolerance
    /method:PSAProjBudgetTolerance.checkBudgetTolerance

What would mean that in \wwwroot\wss\VirtualDirectories\<port number where EP is installed\App_Code\Proxies should be created new stub class called PSAProjBudgetTolerance.cs with method checkBudgetTolerance

The file was not there indeed. If you look into hotfix installation instruction you can see step: “Go to the AX Menu - “Tools” - “Development tools” - “Web development” - “Proxies”. There you can generate proxies directly to server (button Generate). The problem is that if you are not site collection administrator for site where EP is created nothing will happen. The proxies will not be generated and you also not get error. So that was the reason. The proxies did not get generated while new WebControls were already deployed.

To make sure that all components also on Enterprise Portal site got deployed is to run AxUpdatePortal utility: http://msdn.microsoft.com/en-us/library/dd261467.aspx

After running AxUpdatePortal utility creating expense report worked correctly.