Internal error: Entry in COKA-Buffer not found

Hi,

In FB50 I was trying to post the following entries:

760100 (expense/cost element) Dr. 1000

100000 (petty cash account) 1000

When posting (ctrl+s) the following error appears "Internal error: Entry in COKA-Buffer not found". At this point system stops the transaction and exits from that t.code. On expanding the error the following is displayed :

"Internal error: Entry in COKA-Buffer not found

Message no. KC051

Diagnosis

The system could not find the entry with the following key in the COKA float:

Object number = AO00000000000000108166

Cost element = 760100

Origin group =

System Response

An internal error has occurred. Processing stopped.

Procedure

Notify your system administrator."

We checked the table COKA and the above mentioned object no. was not found. So how is the system displaying this particular Object nu.?

Can someone please help to solve this problem?