This is not a problem, like Avada Kedavra said, actually, this is documented here, in the section "Icon Overlay Settings", and I also show bellow. You can read that, and choose the one you like most.
Since it takes quite a while to fetch the status of a working copy, TortoiseSVN uses a cache to store the status so the explorer doesn't get hogged too much when showing the overlays. You can choose which type of cache TortoiseSVN should use according to your system and working copy size here:
Default
Caches all status information in a separate process (TSVNCache.exe). That process watches all drives for changes and fetches the status again if files inside a working copy get modified. The process runs with the least possible priority so other programs don't get hogged because of it. That also means that the status information is not real time but it can take a few seconds for the overlays to change.
Advantage: the overlays show the status recursively, i.e. if a file deep inside a working copy is modified, all folders up to the working copy root will also show the modified overlay. And since the process can send notifications to the shell, the overlays on the left tree view usually change too.
Disadvantage: the process runs constantly, even if you're not working on your projects. It also uses around 10-50 MB of RAM depending on number and size of your working copies.
Shell
Caching is done directly inside the shell extension dll, but only for the currently visible folder. Each time you navigate to another folder, the status information is fetched again.
Advantage: needs only very little memory (around 1 MB of RAM) and can show the status in real time.
Disadvantage: Since only one folder is cached, the overlays don't show the status recursively. For big working copies, it can take more time to show a folder in explorer than with the default cache. Also the mime-type column is not available.
None
With this setting, the TortoiseSVN does not fetch the status at all in Explorer. Because of that, files don't get an overlay and folders only get a 'normal' overlay if they're versioned. No other overlays are shown, and no extra columns are available either.
Advantage: uses absolutely no additional memory and does not slow down the Explorer at all while browsing.
Disadvantage: Status information of files and folders is not shown in Explorer. To see if your working copies are modified, you have to use the “Check for modifications” dialog.