Welcome to the forum. The first thing that I would check is how much free space you have on the working storage drive (usually C:\). Lightroom uses this Working Storage folder (C:\TEMP) to hold temporary files during import. If your drive is full or nearly so, then LR can't get enough space there to hold the temporary files in preparation for import. Usually it is recommended to keep about 100GB free for Working storage files for LR and other apps as well as the Windows Swapfile. Also It might be good to reboot Windows to clear out leftover file that might be stuck in working storage.
You need to be on the latest release of your version of LR. Your forum user profile says LR5 and a subscription. If one is correct, the other probably is not.
To help us sort things out for you, could you go to the LR help menu and click on {System Info...} then copy and paste the contents of that dialog into a reply here.
The only cache that is associated with LR is Camera RAW cache which is used if you shoot RAW file and not JPEGs. or Video Cache which is used with video files. Neither of these are a significant impediment to importing either RAW files or Video Files.
thanks for your attention and help. C drive is almost 14 GB free :/
and this is the system info :
.
Lightroom version: 5.7 [991162]
License type: Perpetual
Operating system: Windows 7 Ultimate Edition
Version: 6.1 [7601]
Application architecture: x86
System architecture: x86
Logical processor count: 2
Processor speed: 3.1 GHz
Built-in memory: 2046.4 MB
Real memory available to Lightroom: 716.8 MB
Real memory used by Lightroom: 394.0 MB (54.9%)
Virtual memory used by Lightroom: 375.8 MB
Memory cache size: 0.0 MB
Maximum thread count used by Camera Raw: 2
System DPI setting: 96 DPI
Desktop composition enabled: Yes
Displays: 1) 1600x900
Application folder: C:\Program Files\Adobe\Adobe Photoshop Lightroom 5.7
Library Path: C:\Users\Karin\Pictures\Lightroom\Lightroom 5 Catalog.lrcat
Settings Folder: C:\Users\Karin\AppData\Roaming\Adobe\Lightroom
Installed Plugins:
1) Behance
2) Canon Tether Plugin
3) Facebook
4) Flickr
5) Leica Tether Plugin
6) Nikon Tether Plugin
Config.lua flags: None
Adapter #1: Vendor : 10de
Device : 641
Subsystem : 562196e
Revision : a1
Video Memory : 1011
AudioDeviceIOBlockSize: 1024
AudioDeviceName: Speakers (Realtek High Definition Audio)
AudioDeviceNumberOfChannels: 2
AudioDeviceSampleRate: 44100
Build: Uninitialized
CardID: 0
Direct2DEnabled: false
GPUDevice: D3D
MaxTexture2DSize: 4096
OGLEnabled: true
Renderer: Software Adapter
ShaderModel: 9.3
Vendor: Unknown
VendorID: 0
Version: 0000:0000:0000:0000