I think, that application, which shows CPU and memory usage (and adds ability to take screenshots and screencasts) has a memory leak. Whe I had it installed after ~12 hours usage phone rejected launching of new applications and said, that I must firstly close something to free memory.
After deinstallation I don't have this issue any more.
But I had deinstalled several other applications, so I'm not sure. And I don't have time right now to investigate the case.