Delay in Entering Data After Calculate

[AK]

After calculating, when I tried to change any cell used by other
formulas, there is a delay of about 5-10 secs before Excel respond
again. The delay goes away and I can enter inputs fine until the next
time I calculate.

Some details:
- Manual calculation set
- Excel 2003 (same problem when opened in Excel 2007 in compatibility
mode)
- File size ~50mb

Initially I thought it was due to the file size but doing a full
calculate only takes 2 sec whereas entering a number after this takes
a far longer time. Though this problem did not appear when the file
size is about 20mb.

Also if I just do a Sheet calculate then I do not have this problem.

I also tried the usual stuff suggested:
- deleting all the formatting and conditional formatting
- removing all add-ins
- setting printer to PDF creator rather than networked printer
- removing all page breaks