Job Cost billing error

Hi All,

   Have a client that has been using Job Cost for years.  They upgraded to 4.50 with service pack 4 some time back.  In the last week when they do job billing they wind up either missing JC_01 or JC_02.  
We have taken the following steps:

We have completely removed the antivirus 
We tried it from more than one workstation
We double checked permissions
We created a new share, installed MAS clean & migrated the data (to be sure the program files were not damaged)

It continues to happen.  We had their IT monitor the files and it shows the files being deleted and created with the exception of one or the other.
Sage has said the only instances of this behavior has been related to AV (which we completely deleted)

Does anyone have any insight or experience with this?   I have seen a lot of things over the years but this is a new one..