Weird table behavior

Hello!
I'm experiencing very strange table behavior while perform queries against it:
1. When I'm doing left join
SELECT [ApprovalId] ,t.ApprovalTypeName FROM [AttendanceApprovals] a left join ApprovalTypes t on t.ApprovalTypeId=a.ApprovalType The ApprovalTypeName is null when the ApprovalType value is 11 (for id from 1 to 10 all works fine), but the value with id=11 is present in the ApprovalTypes table.
2. When I'm trying to delete a row by id:
delete AttendanceApprovals where ApprovalId=21913 it says 0 rows affected but there is row with the id=21913 and the select...where ApprovalId=21913 shows 1 row.
Some days ago all worked fine. I'm not sure what happened and how to fix this. Please, help.
So my table specifications:
CREATE TABLE [dbo].[AttendanceApprovals]( [ApprovalId] [ ...