Theres no specific cure that I know of. There are ways to help stop the blurryness. You can remove the MIP levels from the textures. To do this
1) Get DXTbmp if you dont have it already
(
http://www.mnwright.btinternet.co.uk/download/dxtbmpx.EXE)
2) Open a single texture file from the aircraft you wish to remove mips from. (you may wish just to do the important section, eg wing, tail and fuselage)
3) Make sure the option in DXTbmp for mips is turned OFF (this is on the prefs menu in the older version. and on its own panel on the right hand side in the newer version)
4) Then save this image
Old version:File > Save Extended Bitmap, and set type to either DXT3 (compressed) or 32Bit (uncompressed - clearer)
New Version: File > Save as > Extended bitmap , and set file type to either DXT3 (compressed) or 32Bit (uncompressed - clearer)
5) Repeat from 2) for all textures required.
6)Go fly,
This should aid clarity. If you still get blury textures then it is down to a 'bug' in FS. The only way that I know to avoid it is to zoom in to the max, then back out, this should clear the textures, though the effect my only be tempoary. (Long enough for screenshots etc..)
Hope I've explained that ok, if you need any more help, then post back, or PM me.