[ic] Download error

[DB]

>> Recently I'm getting complaints of customers being unable to download
>> purchased items (pdf files). I did a test purchase and all seems OK if
>> the buyer is logged into an established account. If however they check
>> out without first creating an account, the purchase completes - but when
>> they click the Download button from the receipt page, this error is
>> displyed:
>> 
> 
> Recently means: I have this set up working for months without any problems,
> I did not make any changes to anything on the website and all of a sudden it
> now stopped working ...
> 
> Or did you actually add this as a new feature and it has not worked from the
> beginning? 
> 
> Did you upgrade any parts of your Interchange install?
> 
>> Sorry, there was an error in processing this form action. Please report
>> the error or try again later. (Can't locate object method "new" via
>> package "Vend::UserDB" (perhaps you forgot to load "Vend::UserDB"?) at
>> /usr/local/interchange/lib/Vend/UserDB.pm line 2008. )
>> 
>> I see no errors in my IC logs or in my web server logs. I do see a 200
>> for the pdf in the web server log. I don't have much to go on... does
>> anyone have any thoughts? This is 5.6.3 using a modified foundation store.
>> 
>> DB
> 
> Do you have a development environment?
> 
> If so you can add some debug logging to your process where people click on
> the PDF link, to see what starts happening.
> 
> Perhaps it does a lookup in a cookie, or does check if the user is logged in
> and if not the case tries to call some other things. Is this existing code
> from the foundation, or something written by yourself?

The is code native to foundation. Downloads have been working for years.
The only change I've made somewhat recently is a move from Apache to
Lighttpd. I assumed that since downloads work for logged-in users that
the web server was not to blame. I suppose I could run another test
under Apache to see if it still works that way.