I am currently using the sonar 7 xl home recording studio on a dell xps laptop (intel core i5 processor 2.5 ghz with turbo boost 2.0 up to 3.10 ghz; hard drive 750 gb; memory 8192 mb) using a cakewalk usb audio interface UA-1G soundcard. When laying down multiple tracks I have experienced a problem with latency after opening approximately 20 tracks (most of which only have a brief recording on them).  The tracks begin by sounding fine, however, after approximately 5-6 minutes -when there is very little music recorded- latency then becomes a major problem and the computer stops playing the tracks etc. I have tried experimenting with various ways to dealing with this -outlined in the sonar 7 handbook- but so far with limited success. Anyone have any suggestions as to how to deal with latency? Woud a different soundcard perhaps be one way to resolve this?

Is the soundcard set to ASIO mode? 

Welcome to the forum.
 
This does not seem like what I would generally consider to be latency.  Is this an issue where the playback sound lags behind as you are recording a new track?  Where are you listening when this is happening (echo on tracking in SHS7 or listening on the interface)?  Is this that recorded tracks are just out of sync with previously recorded tracks?  Can you describe more clearly what the problem you are experiencing is assuming that it might not actually be latency?
 
Glen

The audio on the sonar 7 studio is not set to ASIO -I don't know if the soundcard is (I don't see a switch setting for ASIO on the UA-1G). As regards the nature of the problem, what I hear is dropout sounds, or a crackling sound as the recording comes towards the end. All the tracks are in sync, but the sound crackles and eventually the whole thing stops playing etc. I am listening to the recorded tracks through the interface.

This sounds a lot more like you are over-driving the sound card (or a bus or a channel)  to the point that the audio engine is crapping out.  Try turning all of your volumes down (by a bunch) so that you aren't going any where -0dB and see if that makes a difference.
 
Latency is a time thing.  The difference between when a sound goes into the system and how long it takes to come back out.
 
Glen

There isn't a switch for ASIO on the UA-1G.
However, the Advanced Driver Mode switch must be in the ON position (default) to use ASIO.
You select ASIO from within SHS7.
The default here is WDM, which may not offer the best performance with the UA-1G.
Go to Options>Audio>general, and select ASIO in the Driver Mode box.
Click Apply.
Playback Device and Recording Device may reflect some new options.
Make sure the UA-1G is selected for both.
In ASIO driver mode, the latency slider will not work. You must use the ASIO Panel to adjust your latency.

What you are describing isn't latency, But it can happen if the latency is set too low.
It may also be a result of a timing conflict between the built-in sound card and the UA-1G using WDM. 
Selecting ASIO will force SHS7 to use the UA-1G exclusively.

As Glen is suggesting, a drop-out is usually caused by overstressing the system to the point where the audio engine stops. Usually, it's too much activity in too short a time, or a feedback loop.

Some things that can help with the drop-outs and crackling:
Avoid high demand effects while tracking (ie reverbs, compressors).
Low latency is important while recording, but not so much while playing back and editing your mix.
So record at low latency, then increase the latency, and add your effects.
This will give the system more room to breathe.
Watch your levels, in the individual tracks, and in the master bus, where they should all accumulate.
Try these things, and see if it helps.

Many thanks for the information. I have tried setting the UA-1G to the advanced driver mode and changed the appropriate settings in the audio section on sonar 7 (to asio etc). The setting that works best in the asio panel for the music i have recorded is buffer size 10 -the maximum setting (the other settings made the sound more crackly). However, even this did not entirely solve the issue. Would re-recording some of the tracks without effects be one way I might improve the sound? I have tried taking effects off the recorded tracks but this did not have any effect. 

Another place where I have run into problems with popping and crackling sounds is when I have had a project that had multiple sample rates or sample rates that were different than the output device.  I don't recall if SHS7 has the utility to change audio format from the utilities menu, but that might be worth a try.  Try setting the depth to what your interface is set to as an experiment.
 
Glen