Unable to log into Universe Design Tool

When trying to log into our production server from my laptop using Universe Design Tool (UDT) I unexpectedly get this error:

Internal problem

Open Session: Unexpected error

I can access our BO development server using UDT, though.

I can log into BO production using other tools - Webi Rich Client, Report Conversion Tool and Information Design Tool either with my account using Windows AD or as an administrator.

I have cleaned C:\Users\MYACCOUNT\AppData\Roaming\Business Objects\Business Objects 12.0\lsi folder (as found in many suggestions) and restarted SIA and Tomcat with no avail.

BO version: SAP Business Objects 4.1, Service Pack 5

Dell Laptop's OS: Windows 7, service pack 1, 64-bit

Please suggest what can be done!