MSSQLServer vs firebird with XData

hi, im developing a web application with many many users access. Now i'm trying to use Firebird with this sample https://www.youtube.com/watch?v=2SCvzw0L27o but i've Access Violations errors ... 


I want known if Firebird is usable and stable with XDataServer with aurelius OR is better to use MS SQLServer as video sample show ? 
Now i must do a critical choice with DB engine to use !!

Thx

i must use ms-sql server or change to unigui ? please im in a decision period, you must help and suggest me !!!

Firebird should be fine unless you are talking about really really really huge database and simultaneous access, which I believe is not the case?

The Access Violation is probably not related to the technology, but simply something in the code. More info is needed.