Care to elaborate? What kind of problem?
Sure thing.
Initially I used only the basic features of the program (Defrag, Desktop and Logon Background changer, Internet Optimiser) but as I began to like the program I started to use more of its features. After a while though, I began to notice my computer's performance was decreasing (Internet started being slow, Windows took ages to boot, programs took ages to start and crashed with errors) and after some troubleshooting found Tuneup was the cause of my problem.
To begin with it was adding all these functions to start on startup which when I removed using Autoruns just kept coming back. It was also consuming high amounts of CPU (as so many instances of it were opening on startup) which was why my computer started crashing. On top of that its Task Manager was quitting processes required for my other programs (for example I opened up iTunes and in 2 minutes it crashed; I then went into Tuneup's Task Manager and saw it had cancelled the iTunes processes).
So I decided to uninstall Tuneup. And did that take some effort. For starters it refused to be uninstalled through Add or Remove Programs in the Control Panel because it claimed its processes were running. So naturally I went into Task Manager and quit them...and watched them come back before my own eyes...tried to stop them again...they came back again. After multiple attempts to stop them (keeping in mind I couldn't stop them at startup) I attempted to use Revo Uninstaller. After 3 attempts it got there. And my system went back to normal.
I decided that perhaps the copy of Tuneup I had was dodgy so I obtained a different copy but it had the same effect. Perhaps it was my machine that just didn't like Tuneup. Or perhaps I was just unlucky. Unfortunately it ruined the experience.
But I don't want my experience to deter other potential users. It is fantastic program and if you have no troubles when you use it, then enjoy.