I am going to post this in an answer, even though it deals with several possible options and is not specific to the question. This is partly due to the lack of detail provided in the question. For clarity you are using “Windows 7 Home Premium 64 bit” with “the latest LO” (presumably v220.127.116.11). The issue appears to be one of Calc not responding (freezing/hanging) rather than performance degredation, although you are not clear to what degree this may be. I have grouped a few considerations below under these two headings for clarity.
The fact that you suddenly experienced this problem without changing LO (I have inferred this) would suggest that the problem is most likely related to the operating system. This however does not discount the possibility that you have encountered a bug.
In order to determine whether Calc has become unresponsive it can be necessary to leave it for some time (e.g., 30+min or until you receive a system notification) to see if it does eventually respond. Some times other system components need to reach their timeout limits. Have you done this? It can be informative. The print spooler issue you mention in a comment is bug fdo#42673 which is not overly clear in its conclusion. It may have been closed as NOTOURBUG due to being a problem on the network management side of things i.e., CUPS handling of network printers. Most other “print hang” Calc bugs are equally uninformative.
While there are bugs that indicate Calc hanging on fileopen they mainly relate to the XLS/XLSX file formats. Some (like fdo#40650 and fdo#44420 which indicate auto-adjusting row height) are simply not reproducible, which again tends to point to an operating system issue on the user’s computer.
Java should not prevent LO from working as LO is essentially not dependent on Java, however there are instances reported where certain Java versions adversely impact performance. Making sure you have the 32bit version on Windows may help. As you suggest though this should not cause Calc to hang, so I am going to discount this (in this respect).
Indexing / anti-virus services can badly effect performance but should not cause a hang. If possible it can be worth temporarily turning off these services or preventing them from scanning the location you are working from. That will at least discount this possibility.
The memory settings of LO are only applicable to graphic objects. If you have a lot of charts in your spreadsheet then increasing these settings can help, otherwise from a purely calculation perspective these settings will hang no impact.
These bugs indicate some areas that are likely to cause performance issues. All are related things like conditional formatting, filtering, and functions that perform lookup and match type operations. The degree to which they will affect your machine will depend upon their extent:
- fdo#48312, v3.5 series regression, OFFSET(), MATCH(), and HLOOKUP() functions.
- fdo#53576, v3.6 series performance issue / regression, matrix lookup.
- fdo#54887, v3.6 series performance issue / regression, extensive combinations of functions.
- fdo#55269, v3.6 series AutoFilter conflict with the Windows 7 performance option (System Properties > Performance Options) named “Use visual styles on windows and buttons”.
- fdo#61484, v3.6-4.0 series conditional formats performance.
- fdo#63696, v4.0 series performance issue, complex calculations are making Calc unresponsive under more recent version, while earlier versions appear less affected.