If the 650 is a JRMark, it's below average, but not terrible.
Calculated fields can slow things down. Anything that requires getting much data from a remote location will. A virus checker can.
Yup, a calculated field was the perpetrator.
But for me this brings up issues that have been discussed in several other threads. The calculated field was a substitute for the built in field MediaSubType. I made a new calculated field which assigned media sub types to files based on the physical disc location.
In my opinion, the media sub type field is currently severely limited. I'd like to se a field which:
o can use several types of predefined conditions to assign media subtypes
o One should be able to set up a prioritized list of conditions for each media sub type
o A type of condition: File location ("if filename contains Audiobook" etc). This is similar to XBMC's "set Content" functionality
o A type of condition: Set from external, I.e. the field is assigned to, for example by plugins or user input in the views
o There should be a possibility for the user to, at least, add new media sub types
o It should be FAST.