slow spreadsheet in numbers

I only have four Numbers spreadsheets but one is uncomplicated but long; it has about 2400 lines. Some weeks ago it became very, very slow. If I click, the machine is slow to respond; if I type, the data appears 15 seconds of so later. I have read that this has been a problem with Apple for a number of years, but have they come up with a solution? I have a IMAC OS X 10.6.8, the processor is 2 GHz Intel Core 2 Duo, memory is 2 GB 667 MHz DDR2 SCRAM. I have used the disk utility first aid and the problem does not seem to be there. Another community has asked me questions. My capacity reads 250 GB. Under "untitled" it says capacity is 249.72 GB and it states 212.67 is "space free". Page ins are 1.36 GB and page outs are 127.6 MB. I did a disk utility and everything shows ok. In another are it shows page ins are 182.3 MB and page outs are 0 bytes. Everything else on my IMAC works perfectly except for this one spreadsheet. In Activity Monitor I am showing "free" 292.3 MB. No app is using a high percentage of CPU. Numbers is using 106.1 real memory and 72.9 virtual memory.I went into safe mode and that did not alleviate the problem. When I take the cursor into my spreadsheet and click it transforms from a white cross to a hand to a coatrack. It has been suggest that this problem is caused by the fact that my system shows less than 500 MB of RAM. Again, when I click "about this mac" it shows memory is 2 GB 667 MHz. Is this an ongoing problem with Apple Numbers' software or can it be made to work?