1. never use open another screen together with "Screen1", why see here
2. use Do it to check your URL, see also tip 4 here
probably you are in a country, which uses comma as decimal delimiter? if yes, you probably have to convert comma to dot
also the space in the usuario parameter could be a problem, use the Web.UriEncode block to encode the name or write %20 instead of space
3. to use the timer always fires property does not make sense in this case, instead before going to another screen, you should stop the clock, just set clock,TimerEnabled to false
Taifun