[TYPO3-english] Language selector in URL

[Matt Janus]

Hi List,
Could anybody help me with this?

I have a largish site with a single language using RealURL and
occasionally the URL's appear with the following at the end -
?L=iyhhgojcuqjtuixh  .The string of letters is always different.
Clearing the cache manually, seems to resolve this issue but I
amunable to track down the cause.

Could anybody point me in the right direction.

Thanks

Matt