Renato,
The problem with Xbase is that code can compile quite properly and fail quite miserably at runtime. If you are sending the proper arguments to the seek() there is no reason for it to fail. I'd use a combination of code in the Error() method and activating the debugger right before the seek() to trap what's causing the problem.
>Ok thanks to all, but I'm not asking about syntax.
>I'm talking about a strange problem that it's hardly to verify (a syntax error if exist it's always present). The application run well almost of time but sometime that code fail. In my SEEK() I haven't variable for tag or table I use your syntax ( seek( key, "table", "tagname" ) ) .